From the Summary: "For the past 17 fiscal years, beginning with FY1986, the budgetary decisions of Congress and the President have been guided in part by specific goals in statute enforced by a process known as sequestration. The statutory goals initially took the form of deficit targets, but later were changed to limits on discretionary spending (first effective for FY1991) and a 'pay-as-you-go' [PAYGO] requirement for direct spending and revenue legislation (first effective for FY1992). Five sequesters were triggered during years in which Congress and the President did not adhere to these statutory goals. No sequester has occurred, however, since FY1991. In many of the years since FY1991, Congress and the President were able to avoid a sequester by ensuring that it did not enact spending or revenue legislation in violation of the statutory goals. At times, Congress and the President had to take advantage of flexibility in the procedures, such as the ability to designate certain spending as 'emergency requirements,' in order to achieve this outcome. In other instances, however, Congress and the President prevented a sequester that otherwise would have occurred by enacting into law provisions that intervened in the normal operation of the process. […] In the remaining three cases, the statutory intervention resulted in the removal from the PAYGO scorecard of costs that would have led to a $10.5 billion sequester for FY2001 and a $130.279 billion sequester for FY2002, and that might lead to future-year sequesters. In all three instances, the legislative vehicles were annual appropriations acts considered toward the very end of the session (the Consolidated Appropriations Acts for FY2000 and FY2001 and the Defense Appropriations Act for FY2002)."
CRS Report for Congress, RL31155