Such a census has been compiled from the elevation data being sent back by the LOLA instrument on Lunar Reconnaissance Orbiter. It comprises over 5000 craters larger than 20 kilometers in diameter. Some conclusions drawn from an analysis of this crater catalog by members of the LOLA team are described in the September 17, 2010 issue of the journal Science.
This animation illustrates the process of systematically counting craters. Craters larger than 20 kilometers in diameter light up to show color-coded elevation. Some areas, such as the maria and the Orientale basin, are notably sparse, implying that these areas are younger. The processes that formed them erased the record of older impacts visible elsewhere on the Moon.