Bryan,
It doesn't effect static compression ratio, but it does effect dynamic compression.
It also drastically effects cylinder pressure, and the effect varies throughout the RPM range.
Dynamic compression doesn't take into account the ram effect from the moving column of air in the intake which causes cylinder pressure to vary by different amounts at different RPMs.
Have a look at these for a brief overview:
http://members.uia.net/pkelley2/DynamicCR.html
http://www.kb-silvolite.com/calc.php?action=comp
http://www.hcs.harvard.edu/~jus/0303/kuo.pdf
http://www.vehicular.isy.liu.se/~lar...d_2002_SAE.pdf
Kevin