上壘率
The traditional measure of batting performance is considered to be hits divided by the total number of at-bats. Bill James, along with other fathers of sabermetrics, found this measure to be flawed, as it ignores any other way a batter can reach base besides a hit. This led to the creation of the On-base percentage, which takes walks and hit-by-pitches into consideration. To calculate the On-Base percentage, the total number of hits + bases on balls + hit by pitch are divided by at bats + bases on balls + hit by pitch + sacrifice flies.