  Free fermionic construction of four dimensional string vacua, are related to
the Z2XZ2 orbifolds at special points in the moduli space, and yielded the most
realistic three family string models to date. Using free fermionic construction
techniques we are able to classify more than 10^10 string vacua by the net
family and anti-family number. Using a montecarlo technique we find that a bell
shaped distribution that peaks at vanishing net number of chiral families. We
also observe that ~15% of the models have three net chiral families. We find
that in addition to mirror symmetry that the distribution exhibits a symmetry
under the exchange of (spinor plus anti-spinor) representations with vectorial
representations.
