We use data from surveys that ask people how they spend their time. The United States is the only country that collects these statistics every year; the U.S. Bureau of Labor Statistics has been conducting its American Time Use Survey since 2003. To track long-term trends, BEA combines that survey's data with less comprehensive studies that have been conducted occasionally since 1965. BEA uses the wages of general-purpose domestic workers to estimate the value of this unpaid work that people do at home. In addition, when measuring household production, BEA treats consumer purchases of durable goods as investment (these purchases are treated as consumption in GDP).