I found a copy of the relevant class file here; assuming that this is the same as the one that you are using, the culprit is the following comment:
\parskip 0pt % Extra vertical space between paragraphs.
% Set to 0pt outside sections, to keep section heads
% uniformly spaced. The value of parskip is set
% to leading value _within_ sections.
% 12 Jan 2000 gkmt
Sure enough, looking further down in the document we find that in the definition of the section commands, \parskip gets reset. For example:
\def\@ssect#1#2#3#4#5{%
\@tempskipa #3\relax
\ifdim \@tempskipa>\z@
\begingroup
#4{%
\@hangfrom{\hskip #1}%
\interlinepenalty \@M #5\@@par}%
\endgroup
\else
\def\@svsechd{#4{\hskip #1\relax #5}}%
\fi
\vskip -10.5pt %gkmt, 7 jan 00 -- had been -14pt, now set to parskip
\@xsect{#3}\parskip=10.5pt} % within the starred section, parskip = leading 12 Jan 2000 gkmt
That innocuous \parskip=10.5pt at the end means that every time a \section, \subsection, \subsubsection, or \paragraph command is used then \parskip gets reset to 10.5pt. (The command \@sect has the same ending.)
So to reduce \parskip, you need to reduce it each time that you start a section or otherwise. Depending on your needs, a variety of strategies are possible. The simplest would be to have a copy of the class file in the same directory as the TeX file and simply edit out that extra \parskip=10.5pt (actually, edit out both of them: one from \@ssect and one from \@sect). If you need to leave the class file pristine for some reason, then you can redefine these commands in your preamble. The simplest would be to simply copy out the definitions from the class file with the appropriate modifications to \parskip. If you do this, then the copied definitions need to be sandwiched between \makeatletter ... \makeatother.
If you want to be a bit more fancy, you could have the \section commands remember what \parskip is when they are called, then reset it at the end. This would involve hacking three commands from the class file, since the command \@startsection also messes with \parskip. So it would be something like (not tested!):
\makeatletter
\let\orig@startsection=\@startsection
\let\orig@ssect=\@ssect
\let\orig@sect=\@sect
\newskip\orig@parskip
\orig@parskip\parskip % just for safety's sake!
\def\@startsection{%
\orig@parskip\parskip%
\orig@startsection}
\def\@ssect#1#2#3#4#5{%
\orig@ssect{#1}{#2}{#3}{#4}{#5}%
\parskip\orig@parskip}
\def\@sect#1#2#3#4#5#6[#7]#8{%
\orig@sect{#1}{#2}{#3}{#4}{#5}{#6}[#7]{#8}%
\parskip\orig@parskip}
\makeatother
I ran your code. (By the way, your not-so-minimal example doesn't compile unless the natbib and pagenote packages are loaded as well.) At least in the example you provide, there's indeed a problem of "overstretched inter-paragraph glue", confirming @Marco's guess. I can think of three solutions to this problem:
You could issue the following command in your document's preamble:
\raggedbottom
This will let the height of the textblock vary from page to page. If your document is going to be typeset two-sided (aka bookstyle) with facing pages, the result may look poor from a typographic perspective.
A more elegant solution (from a typographic perspective) consists of inserting the command
\usepackage[bottom]{footmisc}
(also in the preamble). Doing so will insert additional whitespace between the main text and the footnote rule rather than over-stretching the inter-paragraph glue. Of course, if a given page doesn't have any footnotes and features a single paragraph break, this approach won't help.
A third and, in my view at least, even better solution would be to break up the text into more but shorter paragraphs. Doing so would increase the text's intelligibility and lessen the risk of an occurrence of the problem you describe.
The example code you provide has an entire page consisting of only two, extremely long paragraphs, plus a rather long footnote. If you were to break up each of these two long paragraphs into two -- better yet, three -- shorter paragraphs, LaTeX would have many more degrees of freedom to play with while building up the page, thereby much reducing the likelihood that LaTeX will have to resort to over-stretching the inter-paragraph glue.
Best Answer
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