union activity. After the Revolution, the Ministry of Labor established the Workers' House to sponsor Islamic unions in large manufacturing concerns. These unions discourage strikes through a combination of cooptation of workers through periodic raises and bonuses and cooperation with authorities to identify and discipline workers who exhibit tendencies toward independence. The Islamic unions generally have been effective in preventing major strikes by workers; a long history of factionalism among different working-class occupational groups and between skilled and unskilled workers within individual industries has contributed to this relative success. Nevertheless, since the early 1990s scattered strikes have defied union control. In some instances, the strikes have been resolved peacefully through negotiations, while in other cases they have been repressed violently by security forces. Lower class The working class is part of the overall urban lower class, or mostazafin, a social stratum that includes all families whose household incomes place them marginally above, at, or below the officially defined poverty line. In cities with populations greater than 250,000, the lower class makes up an average of 40 to 50 percent of the total population; the lower-class proportion generally is less in smaller cities (50,000 to 250,000 population) and towns. In 2010, Iran's Department of Statistics announced that 10 million Iranians live under the absolute poverty line and 30 million live under the relative poverty line. 3 million laborers have been excluded from those statistics, as their data is not registered anywhere. The lower class can be divided into two groups: the marginally poor, who receive regular incomes on a weekly or monthly basis; and the very poor, whose incomes vary from month to month and who thus experience difficulty in paying for food, housing, and utilities. Recipients of regular incomes include pensioners, industrial and construction workers, and people employed in the diverse services sector, such as attendants in barbershops, beauty salons, and public bathhouses, bakery workers, sales clerks, domestic servants, gardeners, garbage and trash collectors, painters and plasterers (of homes), porters, street cleaners, peddlers, street vendors, office cleaners, and laundry workers. These job categories, as well as others, also include at least one million workers who are employed only occasionally or seasonally, primarily as a result of the shortage of full-time positions in an economy that has had an official unemployment rate ranging between 10 and 15 percent of the labor force since the early 1990s. Although many government agencies and