the hidden side of everything

According to the text, the increase if abortion rates triggered the decrease in crime.

".... the states with the highest abortion rates in the 1970s experienced the greatest crime drops in the 1990s, while states with low abortion rates experienced smaller crime drops. (This correlation exists even when controlling for a variety of factors that influence crime: a state's level of incarceration, number of police, and its economic situation.) Since 1985, states with high abortion rates have experienced a roughly 30 percent drop in crime relative to low-abortion states."