Definition:
Static compression ratio is the volume above the piston at bottom dead center divided by the volume of the piston at top dead center. Here's a little picture:


Now there are many factors that affect static compression ratio. Dome/dish size of the piston, combustion chamber size, cylinder bore, stroke, deck height.

As for difference in compression ratios, here they are for integras:
LS (b18b) 9.2:1
GSR (b18c1) 10.0:1
USDM ITR (b18c5) 10.6:1
JDM ITR (b18c) 11.1:1