THE United States, it has often been observed, is a nation defined not by territory or by blood but by ideas. It is also a nation defined, more so than most people realize, by statistics.  The Founders were convinced that the strength of a democracy depended, in no small part, on the shortness of distance between the people and the capital, a belief which dictated the location of Washington, D.C. Additionally, Article I of the Constitution provides for seats in the House of Representatives to be allocated by a decennial census—a radical idea in those days, since no country had ever had a regularly scheduled census before and certainly none had ever seen fit to allot representation in proportion to population. Indeed, I have long thought that the Supreme Court should have used not the equal protection clause of the Fourteenth Amendment but the census clause of Article I for the one-person/one-vote decisions, for the Founders took special and, in their day, unprecedented care to relate representation to population. Statistics have been important ever since.