In the map above, the counties shaded in blue have lost population since 1970. Most of these counties are located in the upper Midwest and Great Plains and represent the bulk of the area that receives federal farm subsidies. While the population of the United States has grown from 203 million in 1970 to 281 million in 2000, a 38.4 percent increase, population growth in the upper Midwest over the same period ranges from 3.6 percent in Iowa to 29.3 percent in Minnesota. Midwestern states have failed to keep up with population growth in the rest of the country. And, within these states, population growth varies greatly from county to county. For example, Iowa has had an overall population growth of 3.6 percent since 1970, but only 28 of the 99 counties have had positive population growth. In the upper Midwest, what characteristics distinguish the counties with population gains from those with population losses?