The U.S. Census Bureau has some of the most interesting data visualizations, many of which help illustrate the magnitude of the data being presented. According to the Bureau, after each decennial census is tabulated, “the Census Bureau calculates the center of population. The National Mean Center of Population based on the 2010 Census is near Plato, Mo., an incorporated village in Texas County.” The mean center is fictitious of course, for the purpose of illustration as the Bureau goes on to explain, “the center is determined as the place where an imaginary, flat, weightless and rigid map of the United States would balance perfectly if all residents were of identical weight.” And the movement is in a southwesterly direction as the interactive map below illustrates: 

What is even more interesting are the suggestions for why the migration has moved in this direction. The Bureau states that the westerly direction has historically been the result of a “sweep [that] reflects the settling of the frontier, waves of immigration and the migration west and south.” But it is fair to say that although the imaginary mean center still resides in the South, a very large and disproportionate part of the population (as well as commerce) has settled in the West in general and California in particular. And there is a clear movement (though not a net loss) from California and the Southwest. The economic and sociological reasons for this would be very interesting to explore.