Origins of "scab"

The SEIU blog has a post on the term "scab." They quote Jack London, Thurgood Marshall and note the 1987 NFL replacements. But the spot on comment recognizes President Reagan validated the use of permanent replacements for strikers by replacing the air traffic controllers in the early 1980's. Money quote:

Reagan's decision was a huge blow to unions and signaled in a shift in the use of strikes. In the decades before 1981, major work stoppages averaged around 300 per year. From 1985 to 1990, the average was 52. By 2006, the average had dropped to less than 30 a year.