A-21 is the number designation given to an OMB (Office of Management and Budget) directive on cost accounting to universities and other institutions that receive federal research grants. This circular lays down rules for grants. It requires the accounting of a university researcher's work to be made in terms of actual time spent, or in terms of a vaguely defined percent of effort.
Most university professors realize that accountability is actually measured by a group of their peers—the group that eventually decides whether or not to recommend approval and funding for the next proposal or extension. Thus tangible results establish that a scientist has done his proposed job—not his hours (or ‘% effort’). The OMB accountants want the books to be kept in hours but will accept percent of effort reports.