 Data for the 4-year completion rate calculations are taken from the Common Core of Data (CCD).The 4-year completion rate calculation is dependent on the availability of dropout estimates over a 4-year span, and current counts of completers.Because dropout rate information was missing for many states during the 4-year period considered by the US Department of Education, 4- year completion rate estimates for the 2000-01 school year are only available for 39 states.