Hubble also instituted a policy of dividing up observing time by size categories, originally into small programs that only needed a handful of hours of Hubble time, and large programs that needed more than 100 hours. The Hubble team had found that the panels that evaluated proposals were reluctant to select large, time-consuming programs because that would limit the diversity of the science Hubble could perform and the number of astronomers who could use the telescope. By designating a pool of time dedicated to large programs, the team avoided penalizing them for the length of their observations. The formula was tweaked over the years to obtain a good distribution of large (75 or more hours), medium (35 to 74 hours) and small (one to 34 hours) programs. Today many observatories, both in space and on the ground, have adopted that approach.