In professional basketball, the most commonly used statistical benchmark for comparing the overall value of players is called efficiency. It is a composite basketball statistic that is derived from basic individual statistics: points, rebounds, assists, steals, blocks, turnovers, and shot attempts. In theory, efficiency accounts for both a player's offensive contributions (points and assists) and their defensive contributions (steals and blocks), but it is generally thought that efficiency ratings favor offense-oriented players over those who specialize in defense, as defense is difficult to quantify with currently tabulated statistics.