Stellar Multiplicity and the Initial Mass Function: Most Stars Are Single

In this Letter I compare recent findings suggesting a low binary star fraction for late-type stars with knowledge concerning the forms of the stellar initial and present-day mass functions for masses down to the hydrogen-burning limit. This comparison indicates that most stellar systems formed in the Galaxy are likely single and not binary, as has been often asserted. Indeed, in the current epoch two-thirds of all main-sequence stellar systems in the Galactic disk are composed of single stars. Some implications of this realization for understanding the star and planet formation process are briefly mentioned.