What causes the ordination shortage?

Over in the comments at Amy Welborn’s, a news report about the arrest of some ex-seminarian (thank Heavens it’s ex-) has become the occasion for the usual misguided souls to blame the shortage of priests on celibacy. They assert such a causal linkage again and again.
However, there is reason to question it: the 2000 Catholic Almanac reports 478 ordinations in the U.S., for a church of about 60 million members. In comparison, the Greek Orthodox Archdiocese, a jurisdiction which of course ordains married men as standard procedure, reports only 8 ordinations in its 2002 yearbook for a church of about 1.5 million members. That is unfortunately a comparable or perhaps even lower rate than that of Catholic ordinations. (I say “perhaps” because one mustn’t put too much weight on the figures of a single year.)
Verdict: the Church’s critics have not proven their case.