[Tex/LaTex] Colorbox not working with longtable

colorlongtable

I have some tables that I want to entirely color in light grey, but the same command lines that work for the tabular environment (see second table example) do not work for the longtable environment (see first table example). How can I color the longtable in the same manner as the tabular table? Thank your for any help!

% PREAMBLE
\documentclass[12pt,a4paper]{article}
\usepackage{longtable}
\setlength{\LTpre}{0pt}
\setlength{\LTpost}{-6pt}
\usepackage{array}
\usepackage[UKenglish]{babel}
\usepackage{geometry}
\usepackage{booktabs}
\usepackage{array}
\usepackage{lscape}
\usepackage{siunitx}
\usepackage{parskip}
\usepackage{xcolor}
\definecolor{lightgray}{gray}{0.8}
\usepackage[skip=2pt,font=scriptsize]{caption}
\newcommand{\oneS}{\ensuremath{{}^{\textstyle *}}}
\newcommand{\twoS}{\ensuremath{{}^{\textstyle **}}}
\begin{document}

% LONGTABLE WHERE COLORBOX IS NOT WORKING
\newgeometry{left=1.5cm,right=1.5cm,top=1.8cm,bottom=1.8cm}
\begin{landscape}
\scriptsize
\thispagestyle{empty}
\scriptsize
%\begingroup\setlength{\fboxsep}{0pt} >>> colorbox commands that return error: Missing \endgroup inserted
%\colorbox{lightgray}{
\begin{longtable}{
  l S[table-format=-1.4] S[table-format=-1.4] S[table-format=-3.2] S[table-format=-5.2] S[table-format= 7.2] S[table-format=-3.2] S[table-format=-3.2] S[table-format=-3.2] S[table-format=-3.2]  @{\hspace{0.8cm}} r r r r } 
\caption{Summary statistics} \label{fig:sumstat} \\
\toprule
{Future i.e. underlying asset}  & \multicolumn{5}{l}{Daily returns on long-only positions} &  \multicolumn{4}{l}{Ljung-Box } & \multicolumn{2}{l}{Avg. vol. (\$ mil.)} &     \multicolumn{2}{l}{Avg. open interest} \\
\cmidrule(r){2-6} \cmidrule(r){7-10} \cmidrule(r){11-12} \cmidrule(r){13-14}
&  {Mean (\%)} & {Std. (\%)} & {Skew. (\%)}  & {Kurt. (\%)} & {Jarque-Bera} & {(5)} & {(20)} & {(60)} & {(120)} & {2000} & {2014} & {2000} & {2014} \\ 
\midrule
\endfirsthead
\toprule
{Future i.e. underlying asset}  & \multicolumn{5}{l}{Daily returns on long-only positions} &  \multicolumn{4}{l}{Ljung-Box } & \multicolumn{2}{l}{Avg. vol. (\$ mil.)} &     \multicolumn{2}{l}{Avg. open interest} \\
 \cmidrule(r){2-6} \cmidrule(r){7-10} \cmidrule(r){11-12} \cmidrule(r){13-14}
&  {Mean (\%)} & {Std. (\%)} & {Skew. (\%)}  & {Kurt. (\%)} & {Jarque-Bera} & {(5)} & {(20)} & {(60)} & {(120)} & {2000} & {2014} & {2000} & {2014} \\ 
\midrule
\endhead
\bottomrule \multicolumn{14}{r}{\emph{Continued on next page}}
\endfoot
\bottomrule
\endlastfoot
Frozen Concentrated Orange Juice    &   -0.0184 &   1.8845  &   -8.68       &   764.51 \twoS    &   3170.82 \twoS   &   20.61   \twoS   &   43.77   \twoS   &   98.60   \twoS   &   150.82  \oneS   &   43  &   37  &   25727   &   16991   \\
\end{longtable}
% }\endgroup >>> colorbox commands that return error: Missing \endgroup inserted
\thispagestyle{empty}
\end{landscape}
\restoregeometry


% TABULAR WHERE COLORBOX IS WORKING
\newgeometry{left=5cm, top=5.3cm,bottom=5.3cm}
\thispagestyle{empty}
\begin{landscape}
\begin{table}[ht]
\scriptsize
\caption{Interest rate term structures }\label{fig:termstruct}
\centering
\begingroup\setlength{\fboxsep}{0pt}
\colorbox{lightgray}{ % >>> same colorbox commands as above working here with tabular environment
\begin{tabular}{ lllccccc }
\toprule
{Country} & {Currency} & {Rates description} & \multicolumn{5}{l}{Availability} \\
\cmidrule(r){3-3} \cmidrule(r){4-8} 
& & {Overnight / Further out} & {O/N} & {1W} & {1M} & {2M} & {3M} \\
\midrule
India   &   INR &   India National Stock Exchange Interbank Offer Rate / INR Swap Onshore OIS   &   x   &   o   &   x   &   x   &   x   \\
\bottomrule
\end{tabular}
}\endgroup % >>> same colorbox commands as above but working here with tabular environment
\end{table}
\end{landscape}
\restoregeometry
\end{document}

Here is a picture of the working (tabular) table colored in grey:
enter image description here

UPDATE (after Christian's solution using tcolorbox)

This seems to be quite tricky.. The coloring now works over multiple pages, but if I adjust the settings such that the caption is not colored the coloring on the second page starts below the top (the same amount I took away on the first page in order not to color the caption -> see pictures). Also the bottomrules are somewhat behind the colors (this is also the case if I choose a very very light grey).

Adjusted line of Christian's solution code:

\begin{tcolorbox}[left=2pt,top=-9pt,boxrule=0pt,boxsep=0pt,arc=0mm,auto outer arc, breakable]

Page one: almost perfect except for the missing bottomrule
enter image description here

Page two: now the color starts below the top
enter image description here

UPDATE (after trying the rowcolor macro)

Unfortunately this still leaves white space around the cmidrules (see picture).

enter image description here

UPDATE (after putting the caption outside the table)

Unfortunately this does not work too. The caption is now excluded (and thus not grey), but the coloring still starts somewhat above the toprule and hence if I move it down the coloring on the second page will start below the toprule.

enter image description here

UPDATE (after properly trying the rowcolor macro with cline instead of cmidrule)

The cmidrule whitespace is gone now, but there are still some things I am not happy about: There is white space where I inserted space between two rows; The continued on next page is also colored in grey; And some significance stars are cut off by the coloring. (This is probably my fault because the table is such a mess and I am sorry for it, but I only started using Latex a very short while ago and I am still a bloody noob). After the picture I will post the whole code of the table as I use it and hopefully you guys find a solution. And btw thanks for all the inputs so far – I really learned a lot from your answers!!

enter image description here

CODE FOR THE TABLE AS OF NOW (after trying rowcolor macro)

\documentclass[12pt,a4paper]{article}
\usepackage{mathpazo}
\usepackage{amsmath}
\usepackage{amsfonts}
\usepackage{latexsym}
\usepackage{graphicx}
\graphicspath{{./eps/}}
\usepackage{longtable}
\setlength{\LTpre}{0pt}
\setlength{\LTpost}{-6pt}
\usepackage{natbib}
\usepackage{array}
\usepackage[applemac]{inputenc}
\usepackage[T1]{fontenc}
\usepackage{lmodern}
\usepackage[UKenglish]{babel}
\usepackage[UKenglish]{isodate}
\usepackage{geometry}
\usepackage{booktabs}
\usepackage{rotating}
\usepackage{tabularx}
\usepackage{array}
\usepackage{lscape}
\usepackage{siunitx}
\usepackage{appendix}
\usepackage{parskip}
\usepackage[table]{xcolor}
\definecolor{lightgray}{gray}{0.9}
\usepackage[skip=2pt,font=scriptsize]{caption}
\newcommand{\oneS}{\ensuremath{{}^{\textstyle *}}}
\newcommand{\twoS}{\ensuremath{{}^{\textstyle **}}}
\begin{document}

% Table 2: Descriptive statistics
\newgeometry{left=1.5cm,right=1.5cm,top=1.8cm,bottom=1.8cm}
\begin{landscape}
\scriptsize
\thispagestyle{empty}
\scriptsize
\def\arraystretch{1.5}
\rowcolors{3}{lightgray}{lightgray}%%%% start with line 3
\begin{longtable}{
l S[table-format=-1.4] S[table-format=-1.4] S[table-format=-3.2] S[table-format=-5.2] S[table-format= 7.2] S[table-format=-3.2] S[table-format=-3.2] S[table-format=-3.2] S[table-format=-3.2] @{\hspace{0.8cm}} r r r r } 
\caption{Summary statistics} \label{fig:sumstat} \\ \hline
{Future i.e. underlying asset}  & \multicolumn{5}{l}{Daily returns on long-only positions} &  \multicolumn{4}{l}{Ljung-Box } & \multicolumn{2}{l}{Avg. vol. (\$ mil.)} &     \multicolumn{2}{l}{Avg. open interest} \\
\cline{2-6} \cline{7-10} \cline{11-12} \cline{13-14}
&  {Mean (\%)} & {Std. (\%)} & {Skew. (\%)}  & {Kurt. (\%)} & {Jarque-Bera} & {(5)} & {(20)} & {(60)} & {(120)} & {2000} & {2014} & {2000} & {2014} \\ 
\hline
\endfirsthead
\hline
{Future i.e. underlying asset}  & \multicolumn{5}{l}{Daily returns on long-only positions} &  \multicolumn{4}{l}{Ljung-Box } & \multicolumn{2}{l}{Avg. vol. (\$ mil.)} &     \multicolumn{2}{l}{Avg. open interest} \\
\cline{2-6} \cline{7-10} \cline{11-12} \cline{13-14}
&  {Mean (\%)} & {Std. (\%)} & {Skew. (\%)}  & {Kurt. (\%)} & {Jarque-Bera} & {(5)} & {(20)} & {(60)} & {(120)} & {2000} & {2014} & {2000} & {2014} \\ 
\hline
\endhead
\hline \multicolumn{14}{r}{\emph{Continued on next page}}
\endfoot
\hline
\endlastfoot
Azuki Red Beans &   -0.0506 &   1.2311  &   -8.48       &   498.31  \twoS   &   581.33 \twoS    &   9.02        &   22.62       &   82.93   \oneS   &   148.58  \oneS   &   256 &   8   &   24081   &   1195    \\
Canola  &   -0.0040 &   1.2639  &   -34.98      &   782.19  \twoS   &   3483.86 \twoS   &   18.63   \twoS   &   78.35   \twoS   &   126.33  \twoS   &   219.49  \twoS   &   35  &   137 &   57000   &   148689  \\
Cocoa   &   0.0152  &   1.9748  &   -22.63      &   526.62  \twoS   &   783.74  \twoS   &   5.05        &   22.98       &   73.80       &   151.80  \oneS   &   58  &   568 &   112073  &   166484  \\
Coffee  &   -0.0628 &   2.0621  &   10.13       &   694.97  \twoS   &   2295.38 \twoS   &   13.29   \oneS   &   38.74   \twoS   &   87.90   \oneS   &   135.62      &   219 &   1'288   &   44670   &   142144  \\
Corn    &   -0.0181 &   1.7912  &   6.17        &   498.40  \twoS   &   579.88  \twoS   &   6.36        &   44.37   \twoS   &   97.27   \twoS   &   168.05  \twoS   &   736 &   5'987   &   428941  &   1033440 \\
Cotton  &   -0.0355 &   1.7950  &   -5.54       &   405.78  \oneS   &   166.01  \twoS   &   17.92   \twoS   &   44.70   \twoS   &   105.17  \twoS   &   187.02  \twoS   &   389 &   961 &   59894   &   171613  \\
Frozen Concentrated Orange Juice    &   -0.0184 &   1.8845  &   -8.68       &   764.51  \twoS   &   3170.82 \twoS   &   20.61   \twoS   &   43.77   \twoS   &   98.60   \twoS   &   150.82  \oneS   &   43  &   37  &   25727   &   16991   \\
Lean Hogs   &   -0.0450 &   1.4720  &   -11.03      &   383.29      &   108.94  \twoS   &   0.15        &   24.79       &   98.73   \twoS   &   177.33  \twoS   &   205 &   1'383   &   49182   &   222955  \\
Live Cattle &   -0.0076 &   0.8947  &   -21.20      &   524.61  \twoS   &   766.75  \twoS   &   11.41   \oneS   &   61.44   \twoS   &   114.85  \twoS   &   219.51  \twoS   &   106 &   2'404   &   35788   &   271159  \\
Lumber  &   -0.0735 &   1.8705  &   14.40       &   290.86      &   13.40   \twoS   &   28.93   \twoS   &   41.23   \twoS   &   91.75   \twoS   &   167.33  \twoS   &   26  &   37  &   3479    &   6036    \\
Milk    &   0.0228  &   0.9491  &   11.11       &   755.16  \twoS   &   3047.50 \twoS   &   38.97   \twoS   &   119.47  \twoS   &   214.46  \twoS   &   277.08  \twoS   &   4   &   60  &   7370    &   17752   \\
Oats    &   0.0215  &   1.9433  &   -15.61      &   548.80  \twoS   &   922.74  \twoS   &   40.62   \twoS   &   65.32   \twoS   &   119.86  \twoS   &   177.37  \twoS   &   9   &   16  &   15592   &   9548    \\
Rapeseed    &   0.0296  &   0.9648  &   -32.82      &   614.05  \twoS   &   1510.62 \twoS   &   42.49   \twoS   &   102.01  \twoS   &   146.87  \twoS   &   196.53  \twoS   &   4   &   135 &   11006   &   52218   \\
Rough Rice  &   -0.0350 &   1.5563  &   2.24        &   438.54  \twoS   &   281.95  \twoS   &   36.49   \twoS   &   52.26   \twoS   &   106.70  \twoS   &   188.64  \twoS   &   8   &   34  &   6573    &   10987   \\
Rubber  &   0.0031  &   2.0663  &   -40.18      &   548.06  \twoS   &   997.78  \twoS   &   4.25        &   49.33   \twoS   &   149.77  \twoS   &   212.53  \twoS   &   1   &   1   &   160418  &   14016   \\
Soybean Meal    &   0.0675  &   1.7365  &   -13.68      &   467.56  \twoS   &   423.02  \twoS   &   4.50        &   33.19   \oneS   &   71.00       &   149.34  \oneS   &   421 &   5'876   &   113168  &   227463  \\
Soybean Oil &   0.0040  &   1.5492  &   10.94       &   502.91  \twoS   &   611.23  \twoS   &   0.77        &   14.75       &   57.70       &   148.56  \oneS   &   208 &   2'311   &   136633  &   272694  \\
Soybean &   0.0384  &   1.5740  &   -20.22      &   490.62  \twoS   &   557.26  \twoS   &   4.41        &   33.68   \oneS   &   88.55   \twoS   &   178.72  \twoS   &   1'266   &   10'905  &   164866  &   456361  \\
Sugar \#11 International    &   0.0143  &   2.0998  &   -31.41      &   494.08  \twoS   &   610.66  \twoS   &   12.69   \oneS   &   28.95       &   108.76  \twoS   &   205.47  \twoS   &   171 &   1'943   &   170865  &   652621  \\
Wheat   &   -0.0375 &   1.9741  &   5.60        &   495.17  \twoS   &   560.82  \twoS   &   0.83        &   26.73       &   91.33   \twoS   &   158.60  \oneS   &   336 &   3'308   &   135389  &   369247  \\
Ultra U.S. Treasury Bond    &   0.0207  &   0.6554  &   -15.76      &   448.51  \twoS   &   338.23  \twoS   &   3.98        &   24.19       &   58.73       &   159.24  \twoS   &   24'011  &   52'455  &   467187  &   630200  \\
Australian Gov't Bond 10Y   &   0.0013  &   0.0686  &   -9.82       &   466.84  \twoS   &   414.14  \twoS   &   12.90   \oneS   &   24.76       &   83.09   \oneS   &   173.44  \twoS   &   1'455   &   5'216   &   165420  &   476535  \\
Australian Gov't Bond 3Y    &   0.0019  &   0.0705  &   10.65       &   558.89  \twoS   &   990.22  \twoS   &   1.45        &   20.53       &   89.57   \twoS   &   162.75  \twoS   &   3'719   &   10'517  &   358211  &   572109  \\
Canadian Gov't Bond 10Y &   0.0153  &   0.3614  &   -14.13      &   466.70  \twoS   &   419.55  \twoS   &   7.15        &   18.00       &   62.10       &   143.37      &   537 &   4'783   &   47155   &   282932  \\
Eurobobl    &   0.0110  &   0.2225  &   -19.45      &   475.48  \twoS   &   474.07  \twoS   &   10.59       &   23.58       &   74.05       &   143.69      &   33'461  &   55'611  &   346668  &   910191  \\
Eurobund    &   0.0154  &   0.3513  &   -9.35       &   451.08  \twoS   &   340.08  \twoS   &   14.25   \oneS   &   26.77       &   74.06       &   130.28      &   82'510  &   93'541  &   642232  &   952275  \\
Euroschatz  &   0.0041  &   0.0885  &   -21.56      &   786.79  \twoS   &   3504.74 \twoS   &   16.06   \twoS   &   41.86   \twoS   &   107.02  \twoS   &   199.08  \twoS   &   22'679  &   36'028  &   305729  &   864832  \\
Japanese Gov't Bond 10Y &   0.0090  &   0.2179  &   -42.09      &   863.28  \twoS   &   4760.13 \twoS   &   8.71        &   29.58       &   91.84   \twoS   &   166.36  \twoS   &   49'603  &   43'313  &   137348  &   91986   \\
Long Gilt   &   0.0104  &   0.3826  &   -1.62       &   509.27  \twoS   &   642.83  \twoS   &   13.67   \oneS   &   30.27       &   79.71   \oneS   &   156.02  \oneS   &   3'535   &   27'988  &   69257   &   355250  \\
Long Swiss Confederation    &   0.0111  &   0.2748  &   -6.38       &   545.83  \twoS   &   889.23  \twoS   &   53.59   \twoS   &   80.77   \twoS   &   126.89  \twoS   &   194.76  \twoS   &   235 &   39  &   14044   &   5847    \\
U.S. Treasury Note 10Y  &   0.0196  &   0.4106  &   -3.10       &   619.08  \twoS   &   1494.68 \twoS   &   8.70        &   35.05   \oneS   &   65.91       &   162.87  \twoS   &   17'967  &   162'889 &   582852  &   2163999 \\
U.S. Treasury Note 2Y   &   0.0068  &   0.1087  &   7.20        &   1168.10 \twoS   &   11061.84    \twoS   &   12.15   \oneS   &   62.03   \twoS   &   112.94  \twoS   &   203.96  \twoS   &   1'166   &   50'400  &   51123   &   915589  \\
U.S. Treasury Note 5Y   &   0.0148  &   0.2694  &   -6.74       &   653.82  \twoS   &   1839.84 \twoS   &   11.64   \oneS   &   41.60   \twoS   &   80.85   \oneS   &   176.22  \twoS   &   9'089   &   83'868  &   400775  &   1719007 \\
Light Sweet Crude Oil (WTI) &   0.0153  &   2.2460  &   -32.40      &   626.96  \twoS   &   1630.41 \twoS   &   11.22   \oneS   &   34.71   \oneS   &   94.42   \twoS   &   160.52  \twoS   &   4'398   &   37'065  &   456534  &   699002  \\
Gasoil  &   0.0516  &   2.0066  &   -19.57      &   554.39  \twoS   &   972.18  \twoS   &   5.35        &   21.43       &   53.77       &   139.47      &   695 &   19'906  &   111039  &   418798  \\
RBOB Gasoline   &   0.0625  &   2.3566  &   -24.29      &   508.62  \twoS   &   673.32  \twoS   &   8.31        &   35.67   \oneS   &   92.23   \twoS   &   163.61  \twoS   &   127 &   1'788   &   88433   &   194846  \\
Heating Oil &   0.0360  &   2.1785  &   -14.55      &   501.86  \twoS   &   610.42  \twoS   &   6.11        &   25.38       &   78.77       &   146.84  \oneS   &   133 &   1'291   &   137530  &   203354  \\
Henry Hub Natural Gas   &   -0.1232 &   3.1845  &   5.43        &   528.06  \twoS   &   764.99  \twoS   &   22.23   \twoS   &   38.98   \twoS   &   85.67   \oneS   &   136.13      &   3'028   &   10'306  &   325705  &   743292  \\
Aluminum    &   -0.0156 &   1.4244  &   -26.87      &   532.39  \twoS   &   834.93  \twoS   &   7.32        &   28.77       &   79.11   \oneS   &   141.59      &   N/A &   6'159   &   7079    &   318966  \\
Copper  &   0.0344  &   1.8510  &   -19.03      &   702.81  \twoS   &   2402.34 \twoS   &   22.34   \twoS   &   67.49   \twoS   &   167.83  \twoS   &   255.37  \twoS   &   231 &   5'112   &   71885   &   128024  \\
Lead    &   0.0394  &   2.1804  &   -22.49      &   615.78  \twoS   &   1493.00 \twoS   &   14.26   \oneS   &   38.81   \twoS   &   87.45       &   189.45  \twoS   &   N/A &   999 &   883 &   40201   \\
Tin &   -0.0011 &   1.9655  &   -15.04      &   571.40  \twoS   &   1094.17 \twoS   &   13.67   \oneS   &   24.79       &   72.21       &   165.87  \twoS   &   N/A &   485 &   1760    &   115101  \\
Nickel  &   0.0235  &   2.4578  &   -12.07      &   644.24  \twoS   &   1747.51 \twoS   &   4.37        &   13.91       &   62.01       &   109.32      &   N/A &   2'184   &   946 &   49631   \\
Zinc    &   -0.0057 &   1.9730  &   -17.62      &   573.15  \twoS   &   1113.17 \twoS   &   14.15   \oneS   &   29.69       &   75.20       &   162.30  \twoS   &   N/A &   2'423   &   1760    &   115101  \\
Gold    &   0.0305  &   1.1971  &   -28.16      &   853.30  \twoS   &   4539.09 \twoS   &   0.62        &   34.75   \oneS   &   87.88   \oneS   &   174.93  \twoS   &   784 &   25'989  &   138832  &   329134  \\
Palladium   &   0.0102  &   2.1923  &   -26.81      &   698.41  \twoS   &   2371.53 \twoS   &   36.51   \twoS   &   55.17   \twoS   &   102.20  \twoS   &   179.60  \twoS   &   14  &   430 &   2193    &   36291   \\
Platinum    &   0.0376  &   1.5101  &   -48.56  \oneS   &   735.37  \twoS   &   2920.08 \twoS   &   17.44   \twoS   &   38.48   \twoS   &   104.69  \twoS   &   156.09  \oneS   &   34  &   932 &   9184    &   59756   \\
Silver  &   0.0250  &   2.0767  &   -96.58  \twoS   &   1048.60 \twoS   &   8771.42 \twoS   &   4.39        &   21.95       &   78.18       &   163.82  \twoS   &   315 &   6'661   &   76057   &   111035  \\
Australian Bank Bill 3M &   0.0005  &   0.0519  &   299.28  \twoS   &   5248.30 \twoS   &   364590.55   \twoS   &   27.00   \twoS   &   72.25   \twoS   &   130.24  \twoS   &   203.28  \twoS   &   2'443   &   4'541   &   411190  &   537365  \\
Canadian Bank Bill 3M   &   0.0024  &   0.0506  &   42.88   \oneS   &   1456.60 \twoS   &   19738.37    \twoS   &   19.17   \twoS   &   49.78   \twoS   &   135.91  \twoS   &   221.26  \twoS   &   1'783   &   3'446   &   205303  &   408228  \\
Euribor 3M  &   0.0012  &   0.0295  &   76.32   \twoS   &   1797.30 \twoS   &   33243.78    \twoS   &   89.68   \twoS   &   152.44  \twoS   &   263.86  \twoS   &   376.17  \twoS   &   28'455  &   32'541  &   1253952 &   1589255 \\
New Zealand Bank Bill 3M    &   0.0011  &   0.0363  &   156.65  \twoS   &   2118.90 \twoS   &   49989.65    \twoS   &   76.46   \twoS   &   155.79  \twoS   &   259.73  \twoS   &   364.35  \twoS   &   220 &   136 &   63039   &   70274   \\
Short Sterling 3M   &   0.0018  &   0.0424  &   17.80       &   1830.90 \twoS   &   34413.00    \twoS   &   59.35   \twoS   &   129.74  \twoS   &   244.83  \twoS   &   363.65  \twoS   &   6'388   &   11'994  &   786150  &   1041323 \\
Eurodollar  &   0.0026  &   0.0431  &   131.20  \twoS   &   2812.70 \twoS   &   93663.21    \twoS   &   116.41  \twoS   &   181.15  \twoS   &   318.82  \twoS   &   392.11  \twoS   &   39'664  &   16'242  &   3136864 &   895134  \\
AEX (Netherlands)   &   -0.0133 &   1.5396  &   -22.67      &   1013.40 \twoS   &   7498.03 \twoS   &   46.31   \twoS   &   86.79   \twoS   &   156.92  \twoS   &   253.75  \twoS   &   1'931   &   2'366   &   41800   &   79304   \\
CAC 40 (France) &   -0.0044 &   1.5408  &   -3.46       &   746.75  \twoS   &   2929.66 \twoS   &   36.11   \twoS   &   66.48   \twoS   &   129.88  \twoS   &   221.36  \twoS   &   5'924   &   5'242   &   351323  &   381862  \\
DAX (Germany)   &   0.0008  &   1.5721  &   -3.70       &   830.23  \twoS   &   4126.65 \twoS   &   28.27   \twoS   &   68.89   \twoS   &   145.43  \twoS   &   230.89  \twoS   &   10'730  &   20'555  &   228371  &   162915  \\
EURO STOXX 50 (Europe)  &   -0.0082 &   1.6192  &   11.02       &   783.26  \twoS   &   3434.34 \twoS   &   50.97   \twoS   &   103.50  \twoS   &   188.80  \twoS   &   288.50  \twoS   &   3'799   &   25'840  &   416090  &   2795034 \\
FTSE MIB (Italy)    &   -0.0156 &   1.5338  &   -26.31      &   833.06  \twoS   &   4210.57 \twoS   &   39.90   \twoS   &   73.75   \twoS   &   148.48  \twoS   &   268.26  \twoS   &   2'309   &   2'052   &   11628   &   45977   \\
FTSE 100 (United Kingdom)   &   -0.0001 &   1.2572  &   -9.71       &   926.07  \twoS   &   5757.65 \twoS   &   59.07   \twoS   &   94.93   \twoS   &   186.20  \twoS   &   321.70  \twoS   &   3'771   &   10'389  &   240624  &   647792  \\
Hang Seng (Hongkong)    &   0.0135  &   1.6649  &   -16.32      &   949.17  \twoS   &   6200.07 \twoS   &   10.32       &   57.15   \twoS   &   120.85  \twoS   &   202.39  \twoS   &   1'619   &   10'961  &   33608   &   121727  \\
IBEX 35 (Spain) &   0.0023  &   1.5751  &   6.20        &   777.89  \twoS   &   3353.76 \twoS   &   20.09   \twoS   &   44.29   \twoS   &   102.28  \twoS   &   188.23  \twoS   &   2'338   &   1'684   &   46959   &   69191   \\
KOSPI 200 (South Korea) &   0.0175  &   1.8296  &   -44.71  \oneS   &   761.27  \twoS   &   3239.77 \twoS   &   9.80        &   32.55   \oneS   &   115.75  \twoS   &   224.64  \twoS   &   3'199   &   21'372  &   36127   &   114246  \\
MSCI Taiwan &   0.0030  &   1.8566  &   -31.66      &   968.52  \twoS   &   6617.40 \twoS   &   46.07   \twoS   &   97.77   \twoS   &   170.87  \twoS   &   262.07  \twoS   &   408 &   1'958   &   25092   &   221379  \\
NASDAQ 100 (U.S.)   &   -0.0089 &   1.9399  &   7.76        &   903.03  \twoS   &   5339.96 \twoS   &   31.70   \twoS   &   93.67   \twoS   &   199.40  \twoS   &   322.55  \twoS   &   7'312   &   281 &   35905   &   9260    \\
Nikkei 225 (Japan)  &   -0.0063 &   1.6453  &   -12.16      &   874.19  \twoS   &   4846.92 \twoS   &   27.41   \twoS   &   49.96   \twoS   &   115.91  \twoS   &   200.30  \twoS   &   151 &   1'290   &   15735   &   67237   \\
S\&P Toronto 60 (Canada)    &   0.0125  &   1.2849  &   -58.78  \oneS   &   1156.30 \twoS   &   10962.79    \twoS   &   32.43   \twoS   &   61.59   \twoS   &   142.15  \twoS   &   230.70  \twoS   &   573 &   1'539   &   63260   &   144992  \\
S\&P 500 (U.S.) &   0.0040  &   1.3219  &   -2.63       &   1282.40 \twoS   &   14163.06    \twoS   &   38.01   \twoS   &   82.31   \twoS   &   173.96  \twoS   &   261.28  \twoS   &   19'130  &   4'015   &   403594  &   182424  \\
IPC (Mexico)    &   0.0228  &   1.4116  &   -0.59       &   880.18  \twoS   &   4939.79 \twoS   &   34.95   \twoS   &   73.64   \twoS   &   124.08  \twoS   &   195.83  \twoS   &   1   &   169 &   1086    &   55327   \\
Bovespa (Brazil)    &   -0.0135 &   1.8909  &   -26.57      &   606.92  \twoS   &   1423.80 \twoS   &   13.67   \oneS   &   58.73   \twoS   &   101.27  \twoS   &   178.58  \twoS   &   204 &   2'389   &   27676   &   312498  \\
MSCI Singapore  &   0.0085  &   1.4114  &   -43.15  \oneS   &   1001.30 \twoS   &   7326.78 \twoS   &   14.36   \oneS   &   64.26   \twoS   &   137.04  \twoS   &   247.84  \twoS   &   81  &   595 &   4123    &   56762   \\
AUD/USD &   0.0079  &   0.8860  &   -43.54  \oneS   &   1158.80 \twoS   &   10933.65    \twoS   &   19.48   \twoS   &   58.86   \twoS   &   131.11  \twoS   &   241.61  \twoS   &   N/A &   N/A &   N/A &   N/A \\
EUR/USD &   0.0085  &   0.6700  &   9.27        &   463.11  \twoS   &   395.45  \twoS   &   6.31        &   22.59       &   67.66       &   152.46  \oneS   &   N/A &   N/A &   N/A &   N/A \\
GBP/USD &   0.0004  &   0.5929  &   -45.30  \oneS   &   736.82  \twoS   &   2920.61 \twoS   &   3.35        &   40.97   \twoS   &   136.90  \twoS   &   239.83  \twoS   &   N/A &   N/A &   N/A &   N/A \\
NZD/USD &   0.0124  &   0.8917  &   -41.20      &   587.22  \twoS   &   1310.25 \twoS   &   7.39        &   23.55       &   84.87       &   172.86  \twoS   &   N/A &   N/A &   N/A &   N/A \\
BRL/USD &   -0.0074 &   1.1436  &   -49.34  \oneS   &   1024.00 \twoS   &   7834.59 \twoS   &   19.81   \twoS   &   58.41   \twoS   &   130.30  \twoS   &   191.40  \twoS   &   N/A &   N/A &   N/A &   N/A \\
CAD/USD &   0.0087  &   0.5996  &   -10.18      &   622.54  \twoS   &   1532.79 \twoS   &   18.68   \twoS   &   50.68   \twoS   &   130.16  \twoS   &   229.81  \twoS   &   N/A &   N/A &   N/A &   N/A \\
CHF/USD &   0.0160  &   0.7299  &   -22.03      &   1218.40 \twoS   &   12404.99    \twoS   &   7.54        &   44.20   \twoS   &   105.18  \twoS   &   191.89  \twoS   &   N/A &   N/A &   N/A &   N/A \\
INR/USD &   -0.0102 &   0.4514  &   -83.39  \twoS   &   1750.20 \twoS   &   31272.79    \twoS   &   22.96   \twoS   &   45.01   \twoS   &   138.67  \twoS   &   287.85  \twoS   &   N/A &   N/A &   N/A &   N/A \\
JPY/USD &   -0.0005 &   0.6857  &   49.31   \oneS   &   1099.90 \twoS   &   9532.93 \twoS   &   11.25   \oneS   &   36.77   \oneS   &   101.95  \twoS   &   151.66  \oneS   &   N/A &   N/A &   N/A &   N/A \\
KRW/USD &   0.0018  &   0.7174  &   62.96   \twoS   &   5505.20 \twoS   &   397837.97   \twoS   &   22.50   \twoS   &   142.56  \twoS   &   370.24  \twoS   &   534.95  \twoS   &   N/A &   N/A &   N/A &   N/A \\
MXN/USD &   -0.0088 &   0.7140  &   -74.34  \twoS   &   1423.20 \twoS   &   18837.97    \twoS   &   22.67   \twoS   &   62.23   \twoS   &   128.15  \twoS   &   198.38  \twoS   &   N/A &   N/A &   N/A &   N/A \\
NOK/USD &   0.0077  &   0.8140  &   -9.00       &   576.40  \twoS   &   1125.91 \twoS   &   5.39        &   29.01       &   98.07   \twoS   &   181.81  \twoS   &   N/A &   N/A &   N/A &   N/A \\
PLN/USD &   0.0088  &   0.9634  &   -39.42      &   773.60  \twoS   &   3382.81 \twoS   &   11.68   \oneS   &   52.42   \twoS   &   118.06  \twoS   &   249.66  \twoS   &   N/A &   N/A &   N/A &   N/A \\
SEK/USD &   0.0076  &   0.8347  &   0.29        &   598.55  \twoS   &   1307.98 \twoS   &   8.89        &   34.02   \oneS   &   98.45   \twoS   &   221.08  \twoS   &   N/A &   N/A &   N/A &   N/A \\
SGD/USD &   0.0077  &   0.3432  &   7.99        &   817.99  \twoS   &   3941.20 \twoS   &   4.41        &   29.67       &   85.70   \oneS   &   154.16  \oneS   &   N/A &   N/A &   N/A &   N/A \\
TRY/USD &   -0.0383 &   1.3971  &   -668.12 \twoS   &   13878.00    \twoS   &   2731629.47  \twoS   &   28.88   \twoS   &   65.38   \twoS   &   173.38  \twoS   &   310.09  \twoS   &   N/A &   N/A &   N/A &   N/A \\
ZAR/USD &   -0.0152 &   1.1655  &   -109.65 \twoS   &   1467.00 \twoS   &   20691.50    \twoS   &   6.60        &   34.75       &   60.13       &   130.08      &   N/A &   N/A &   N/A &   N/A \\
\end{longtable}
\noindent {\em Notes:} The Jarque-Bera statistic tests the null hypothesis that the daily returns are normally distributed. The Ljung-Box statistic tests the null hypothesis that daily return residuals exhibit no autocorrelation for a fixed number of lags (L). The average dollar volume is the notional value of contracts for all maturity months traded on an average day, defined as: number of contracts traded x futures price x multiplier x exchange rate. There is no volume and open interest data for the currency futures because they were constructed as forwards from spot exchange rates and the country specific interest rate term structure (see further appendix). Volume and open interest data for contracts from the London Metals Exchange (LME) is only available from mid September 2005 onwards. 
\noindent \begin{tabular}{  r @{\hspace{0.1cm}} l }
  * & Indicate statistical significance at the 5\% level. \\
  ** &  Indicate statistical significance at the 1\% level. \\
\end{tabular}
\thispagestyle{empty}
\end{landscape}
\restoregeometry
\end{document}

Best Answer

Perhaps this is, what the OP requests, but I could not test any feature, since the example by the OP is fragmented. I changed to tcolorbox with no rounded corners and switched off the box rules. In order to demonstrate the colorbox at all, I used a yellow background colour.

\documentclass[12pt,a4paper]{article}
\usepackage{longtable}
\setlength{\LTpre}{0pt}
\setlength{\LTpost}{-6pt}
\usepackage{array}
\usepackage[applemac]{inputenc}
\usepackage[T1]{fontenc}
\usepackage{lmodern}
\usepackage[UKenglish]{babel}
\usepackage[UKenglish]{isodate}
\usepackage{geometry}
\usepackage{booktabs}
\usepackage{array}
\usepackage{lscape}
\usepackage{siunitx}
\usepackage{parskip}
\usepackage{xcolor}
\usepackage{tcolorbox}%
\definecolor{lightgray}{gray}{0.98}
\usepackage[skip=2pt,font=scriptsize]{caption}
\newcommand{\oneS}{\ensuremath{{}^{\textstyle *}}}
\newcommand{\twoS}{\ensuremath{{}^{\textstyle **}}}

\tcbuselibrary{breakable}


\begin{document}%

\newgeometry{left=1.5cm,right=1.5cm,top=1.8cm,bottom=1.8cm}
\begin{landscape}
\scriptsize
\thispagestyle{empty}
\scriptsize
%\begingroup\setlength{\fboxsep}{0pt} >>> NOT WORKING returns "Missing \endgroup inserted" error
%\colorbox{lightgray}{
\begin{tcolorbox}[boxrule=0pt,colback=yellow,oversize=1cm,arc=0mm,auto outer arc, breakable]
\begin{longtable}{%
l S[table-format=-1.4] S[table-format=-1.4] S[table-format=-3.2] S[table-format=-5.2]
S[table-format= 7.2] S[table-format=-3.2] S[table-format=-3.2] S[table-format=-3.2] 
S[table-format=-3.2]  @{\hspace{0.8cm}} r r r r } 
\caption{Summary statistics} \label{fig:sumstat} \\
\toprule
{Future i.e. underlying asset}  & \multicolumn{5}{l}{Daily returns on long-only 
positions} &  \multicolumn{4}{l}{Ljung-Box } & \multicolumn{2}{l}{Avg. vol. (\$ mil.)} 
& \multicolumn{2}{l}{Avg. open interest} \\
\cmidrule(r){2-6} \cmidrule(r){7-10} \cmidrule(r){11-12} \cmidrule(r){13-14}
&  {Mean (\%)} & {Std. (\%)} & {Skew. (\%)}  & {Kurt. (\%)} & {Jarque-Bera} & {(5)} & 
{(20)} & {(60)} & {(120)} & {2000} & {2014} & {2000} & {2014} \\ 
\midrule
\endfirsthead
\toprule
{Future i.e. underlying asset}  & \multicolumn{5}{l}{Daily returns on long-only 
positions} &  \multicolumn{4}{l}{Ljung-Box } & \multicolumn{2}{l}{Avg. vol. (\$ mil.)} 
& \multicolumn{2}{l}{Avg. open interest} \\
\cmidrule(r){2-6} \cmidrule(r){7-10} \cmidrule(r){11-12} \cmidrule(r){13-14}
&  {Mean (\%)} & {Std. (\%)} & {Skew. (\%)}  & {Kurt. (\%)} & {Jarque-Bera} & {(5)}
&     {(20)} & {(60)} & {(120)} & {2000} & {2014} & {2000} & {2014} \\ 
\midrule
\endhead
\bottomrule \multicolumn{14}{r}{\emph{Continued on next page}}
\endfoot
\bottomrule
\endlastfoot
Frozen Concentrated Orange Juice    &   -0.0184 &   1.8845  &   -8.68       &   764.51
\twoS   &   3170.82 \twoS   &   20.61   \twoS   &   43.77   \twoS   &   98.60   \twoS
&   150.82  \oneS   &   43  &   37  &   25727   &   16991   \\
\end{longtable}
\end{tcolorbox}%
% }\endgroup >>> NOT WORKING returns "Missing \endgroup inserted"error
\thispagestyle{empty}
\end{landscape}
\restoregeometry   

\end{document}%

The screen shot shows a version, where I copied the last table line to blow up the table for next page, but for sake of shortness, I do not post this repetion in this example here.

enter image description here

Edit -- Update As the OP requested:

A more tight colorbox around the table, with a grey background colour, in order to keep the post small, I will only give the change -- replace this in my above example.

In the preamble use

\usepackage{caption}

At the relevant place just before \begin{longtable} use for the tightest tcolorbox around the table itself.

\captionof{table}{Summary statistics} \label{fig:sumstat}
\begin{tcolorbox}[left=2pt,top=0pt,boxrule=0pt,bottom=0pt,boxsep=0pt,colback=gray,arc=0mm,auto outer arc, breakable]

enter image description here