The results of the FCRAO Extragalactic CO Survey are used to examine the tr
ends in the global star formation efficiency among galaxies as a function o
f galaxy size and environment. For isolated spiral galaxies, Virgo cluster
spiral galaxies, pairs, and field spiral galaxies, an intriguing new result
indicates that the global star formation efficiency decreases as the galax
y size increases. The galaxies in these diverse environments all exhibit th
e same trend in that the mean global star formation efficiency is 4 times s
maller in galaxies 100 kpc in diameter compared to those only 10 kpc across
. This trend may result from a greater shear in the disks of large galaxies
, in which flat rotation curves are found, in contrast to the disks of smal
ler galaxies, in which rotation curves are rising over most of the disk. Th
is shear would be expected to increase the turbulent energy in molecular cl
ouds and to possibly reduce the efficiency of star formation. In sharp cont
rast to this trend of decreasing star formation efficiency with increasing
galaxy size, the galaxies that are independently recognized to be merger re
mnants all display a completely different behavior in the star formation ef
ficiency variation with galaxy size. At every galaxy size, the merger remna
nts display the largest star formation efficiencies observed. Furthermore,
there appears to be a maximum star formation efficiency that merger remnant
s can maintain.