The Hall 's board of directors selects a committee of 16 voters for each era , made up of Hall of Famers , executives , baseball historians , and media members .
Each of the three groups is made up of Hall of Famers , baseball executives , media members , and baseball historians , and votes on people who made their greatest contributions in a different era of baseball : Each of these three groups votes once every three years , and they rotate in the order listed above .