Marketers define people by income, age, profession, etc. In the process, they may overlook one of the most important ways in which Americans define themselves: by their involvement in volunteer work. A report by the Bureau of Labor Statistics says 64.5 million Americans engaged in volunteer work at least once from September 2003 to September 2004. (It defines volunteers as those who do unpaid work through or for an organization, thus excluding ad hoc individual efforts.) For many people, volunteering is a major commitment. Those who did volunteer work during the period covered by the study spent a median of 52 hours at it. Despite the time pressures of child-rearing, the incidence of volunteering was highest among people in the prime parental years (see the chart). Thirty percent of Americans who volunteered did so for two or more organizations. Such multiple efforts were more common among people with high levels of education than among those who are less educated. Religious institutions were the most frequent venues for people's volunteer work, followed by those related to education/youth services, social- and community-service organizations, and hospitals and other health organizations.