As one textbook produced for use in Texas schools has openly acknowledged, Texas counties are prone to inefficient operations and are vulnerable to corruption, for several reasons. First, most of them do not have a merit system but operate on a spoils system, so that many county employees obtain their positions through loyalty to a particular political party and commissioner rather than whether they actually have the skills and experience appropriate to their positions. Second, most counties have not centralized purchasing into a single procurement department which would be able to seek quantity discounts and carefully scrutinize bids and contract awards for unusual patterns. Third, in 90 percent of Texas counties, each commissioner is individually responsible for planning and executing their own road construction and maintenance program for their own precinct, which results in poor coordination and duplicate construction machinery.