typically produced a wide range of crop, garden, and animal products—all requiring substantial labor—large industrial farms typically specialize in just a few crop or livestock varieties, using large machinery and high-density livestock containment systems that require a fraction of the labor per unit produced. For example, Iowa State University reports the number of hog farmers in Iowa dropped from 65,000 in 1980 to 10,000 in 2002, while the number of hogs per farm increased from 200 to 1,400. The consolidation of the feed, seed, processed grain, and livestock industries has meant that there are fewer small businesses in rural areas. This decrease in turn exacerbated the decreased demand for labor. Rural areas that used to be able to provide employment for all young adults willing to work in challenging conditions, increasingly provide fewer opportunities for young adults. The situation is made worse by the decrease in services such as schools, business, and cultural opportunities that accompany the decline in population, and the increasing age of the remaining population further stresses the social service system of rural areas. Abandonment of small towns The rise of corporate agricultural structures directly affects small rural communities, resulting in decreased populations, decreased incomes for some segments, increased income inequality, decreased community participation, fewer retail outlets and less retail trade, and increased environmental pollution. Since the 1990s, China has merged schools into more centralized village-, town-, or county-level schools in rural areas to address some of these very problems. Determinants of rural flight There are several determinants, push and pull, that contribute to rural flight: lower levels of (perceived) economic opportunity in rural communities versus urban ones, lower levels of government investment in rural communities, greater education opportunities in cities, marriages, increased social acceptance in urban areas, and higher levels of rural fertility. Economic determinants Some migrants choose to leave rural communities out of the desire to pursue greater economic opportunity in urban areas. Greater economic opportunities can be real or perceived. According to the Harris-Todaro Model, migration to urban areas will continue as long as "expected urban real income at the margin exceeds real agricultural product" (127). However, sociologist Josef Gugler points out that while individual benefits of increased wages may outweigh the costs of migration, if enough individuals follow this rationale, it can produce harmful effects such as overcrowding and unemployment on a national level. This phenomenon, when the rate of urbanization outpaces the