The current pattern for distribution of seats began with the legislative apportionment plan of 1972 and has been revised every ten years thereafter according to the results of the decennial U.S. Census. A Constitutional amendment, the plan created 47 legislative districts, many of which cross county boundaries to delineate districts relatively equal in population. Each legislative district elects one senator and three delegates. Some of the larger districts are divided into delegate subdistricts to provide local representation to areas not large enough to constitute an entire legislative district.