(The Guttmacher Institute)

As 2010 ended, Means told her office landlord of her plans. Word leaked and protesters materialized quickly. Posters circulated with her picture on one side scrawled with the words “child abuser”; the other side urged protesters to “reach out” to her at her home and office.

A letter arrived from an antiabortion activist who befriended Scott Roeder, the man convicted of killing Tiller, after he went to prison. That letter, now in federal hands, warned Means to check under her yellow Mini Cooper for explosives before turning the key.

The pressure on Means was unrelenting. Her business manager quit, patients fled. A feminist group offered her a bulletproof vest. Law enforcement officials briefed her staff on how to spot a bomb.

This story could help explain why, over the past few decades, the number of abortion providers has declined: The vast majority of doctors don’t want to wear a bulletproof vest to work. And they don’t have to. Many abortion providers do. The biggest decline in their ranks was through the 1990s. During a wave of anti-abortion violence then — three doctors killed in five years — the number of providers dropped from 2,680 in 1985 to 1,787 in 2005. The number of abortion providers has held steady in the early 2000s as violence subsided: Tiller’s 2009 slaying was the first shooting of an abortion provider in more than a decade.

Abortion has also become increasingly non-hospital based, performed in stand-alone clinics, making providers easier to target.

When doctors have an array of career choices that don’t require training on bomb preparedness, providing abortions is a difficult professional decision to make.