Does contraception reduce "unwanted" pregnancies?

Writing in The Wall Street Journal, James Taranto traces the history of "the pill," and notes that after the Food and Drug Administration approved it in 1960 "the marriage rate declined and the illegitimacy rate skyrocketed," evidence to which Charles Murray pointed in the same publication.  Before 1960, the illegitimate birth rate was about 2% of white births; by 2008, it was 44%.  The rates, says Murray, are higher for black births.

Taranto counters the claim that contraception decreases unwanted pregnancy:

The usual criticism we've heard is that it is absurd to suggest a causal link between birth-control advances and illegitimacy because, after all, birth control prevents pregnancy, and giving birth out of wedlock entails pregnancy. By that logic, though, illegitimacy rates should have remained low, or even declined further, after the inception of the pill. The Santorum argument may be counterintuitive, but the counterargument flies in the face of the facts.

It is this reality that Taranto says is often thought of today as "downright unthinkable." Be sure to read his entire article.