The United States hospital industry is an unusual market in that nonprofit and for-profit producers exist simultaneously. Theoretical literature offers conflicting views on whether nonprofit hospitals are less financially efficient. Theory suggests that nonprofit hospitals are so much more interested in offering high-quality service than in making money that they frequently input more resources to provide the same output of service as for-profit hospitals. This priority might also often lead them to be less vigilant in streamlining their services--eliminating duplication between departments, for instance. Conversely, while profit motive is thought to encourage for-profit hospitals to attain efficient production, most theorists admit that obstacles to that efficiency remain. For-profit hospital managers, for example, generally work independently of hospital owners and thus may not always make maximum financial efficiency their highest priority. The literature also suggests that widespread adoption of third-party payment systems may eventually eliminate any such potential differences between the two kinds of hospitals.

The same literature offers similarly conflicting views of the efficiency of nonprofit hospitals from a social welfare perspective. Newhouse (1970) contends that nonprofit hospital managers unnecessarily expand the quality and quantity of hospital care beyond the actual needs of the community, while Weisbrod (1975) argues that nonprofit firms--hospitals included--contribute efficiently to community welfare by providing public services that might be inadequately provided by government alone.

    While acknowledging that there are greater employment opportunities for Latin Ameri can women in cities than in the countryside, social science theorists have continued to argue that urban migration has unequivocally hurt women's status. However, the effects of migration are more complex than these theorists presume. For example, effects can vary depending on women's financial condition and social class. Brazilian women in the lowest socioeconomic class have relatively greater job opportunities and job security in cities than do men of the same class, although there is no compelling evidence that for these women the move to the city is a move out of poverty. Thus, these women may improve their status in relation to men but at the same time may experience no improvement in their economic standing.

    In addition, working outside the home, which is more common in urban than in rural areas, helps women in the lowest socioeconomic class make contacts to extend exchange networks—the flow of gifts, loans, or child care from those who currently have access to resources to those who do not. Moreover, poor women working in urban areas actively seek to cultivate long-term employeremployee relations. When an emergency arises that requires greater resources than an exchange network can provide, these women often appeal for and receive aid from their wealthy employers. However, the structure of many poor women's work—often a labor force of one in an employer's home—makes it difficult for them to organize to improve their economic conditions in general.

    Not surprisingly, then, Latin American women in the lowest socioeconomic class differ in their opinions about the effects of urban migration on their lives. Some find urban living, with access to electricity and running water, an improvement and would never return to the countryside. Others, disliking the overcrowding and crime, would return to the countryside if there were work opportunities for them there. Thus, urban life has had both negative and positive impacts on women's lives. In general, urban migration has not provided economic prosperity or upward mobility for women in the lowest socioeconomic class, despite their intelligent and energetic utilization of the resources available to them.

Although numbers of animals in a given region may fluctuate from year to year, the fluctuations are often temporary and, over long periods, trivial. Scientists have advanced three theories of population control to account for this relative constancy.

The first theory attributes a relatively constant population to periodic climatic catastrophes that decimate populations with such frequency as to prevent them from exceeding some particular limit. In the case of small organisms with short life cycles, climatic changes need not be catastrophic: normal seasonal changes in photoperiod (daily amount of sunlight), for example, can govern population growth. This theory — the density-independent view — asserts that climatic factors exert the same regulatory effect on population regardless of the number of individuals in a region.

A second theory argues that population growth is primarily density-dependent — that is, the rate of growth of a population in a region decreases as the number of animals increases. The mechanisms that manage regulation may vary. For example, as numbers increase, the food supply would probably diminish, which would increase mortality. In addition, as Lotka and Volterra have shown, predators can find prey more easily in high-density populations. Other regulators include physiological control mechanisms: for example, Christian and Davis have demonstrated how the crowding that results from a rise in numbers may bring about hormonal changes in the pituitary and adrenal glands that in turn may regulate population by lowering sexual activity and inhibiting sexual maturation. There is evidence that these effects may persist for three generations in the absence of the original provocation. One challenge for density-dependent theorists is to develop models that would allow the precise prediction of the effects of crowding.

A third theory, proposed by Wynne-Edwards and termed "epideictic," argues that organisms have evolved a "code" in the form of social or epideictic behavior displays, such as winter-roosting aggregations or group vocalizing; such codes provide organisms with information on population size in a region so that they can, if necessary, exercise reproductive restraint. However, Wynne? Edwards’s theory, linking animal social behavior and population control, has been challenged, with some justification, by several studies.