  Recent HST observations of a large sample of globular clusters reveal that
every cluster contains between 40 and 400 blue stragglers. The population does
not correlate with either stellar collision rate (as would be expected if all
blue stragglers were formed via collisions) or total mass (as would be expected
if all blue stragglers were formed via the unhindered evolution of a subset of
the stellar population). In this paper, we support the idea that blue
stragglers are made through both channels. The number produced via collisions
tends to increase with cluster mass. In this paper we show how the current
population produced from primordial binaries decreases with increasing cluster
mass; exchange encounters with third, single, stars in the most massive
clusters tend to reduce the fraction of binaries containing a primary close to
the current turn-off mass. Rather their primaries tend to be somewhat more
massive (~1-3 M_sun) and have evolved off the main sequence, filling their
Roche lobes in the past, often converting their secondaries into blue
stragglers (but more than 1 Gyr or so ago and thus they are no longer visible
as blue stragglers). We show that this decline in the primordial blue straggler
population is likely to be offset by the increase in the number of blue
stragglers produced via collisions. The predicted total blue straggler
population is therefore relatively independent of cluster mass, thus matching
the observed population. This result does not depend on any particular assumed
blue straggler lifetime.
