The reallocation of seats or redrawing of constituencies is very often based on the results of the preceding census which inform the competent body of population changes which have occurred and which can then be addressed by redrawing boundaries or reallocating seats to restore equal voting power. Countries like Belgium, Bulgaria, Costa Rica, Denmark, France, Greece, Italy, Ireland, Switzerland, Turkey and the United States all opt for this system. Notably, these changes are made at different time intervals and with some variations among countries. Substantively, however, all changes are based on census results.