That America has become more politically polarized in recent decades is a widely accepted notion, and though some observers dispute aspects of this trend, political scientists have found strong overall evidence to support it.

Large gatherings such as concerts, sporting events, religious ceremonies and demonstrations are an essential part of a society’s vibrant public life and traditions, but they also carry risks. Participants can suffer from stress-related illnesses or sustained exposure to extreme temperatures, and even be injured or die as a result of uncontrolled crowd behaviors.

Racial profiling and discrimination against African-American youth by police are problems that periodically grab national attention. Yet there is seldom subtle discussion of whether such discrimination is more prevalent in predominantly black or white neighborhoods, or in mixed racial settings. Moreover, data from black adolescents themselves who may face these realities are infrequently collected, analyzed and cited.

The debate over charter schools shows few signs of receding as a central component in the discussion about improving U.S. public education. While proponents see charter schools as a vital source of innovation in public education, opponents feel they are largely ineffective and operate at the expense of large numbers of students. To complicate matters, previous research about the impact of charter schools on student achievement has uncovered mixed results.

As supply chains stretch around the globe, scrutiny of working conditions in distant factories has increased. But international labor standards often depend on corporations engaging in “private voluntary regulation,” and even when such standards are adhered to, factory floor dynamics may determine their actual effectiveness.

According to a 2011 U.S. Bureau of Statistics study, the proportion of women working outside the home increased more than 20% between 1970 and 2010, rising from 39% to 47% of the population. And more of these women hold better-paying positions than they did two generations ago.