ment—date from Kuznets's work in the 1930s. The NIPA aggregates are analogous to a firm's income statement in that they represent economic activity for a period of time, usually a quarter or a year. Over the next decade the accounts were elaborated and redefined. The basic framework delineated in 1947 is discussed in Kuznets (1948c) and has, with a few exceptions, remained virtually intact since that time. The major aggregates today are GDP and expenditure, national income, personal income, and personal disposable income. The nation's asset accounts, analogous to a firm's balance sheet, have also been developed as part of the national accounts. The most developed is a set of capital asset accounts, reflecting a component of the nation's wealth.
As noted earlier, the traditional national accounts include primarily the final output of marketed goods and services—that is, of goods and services that are bought and sold in market transactions. Notwithstanding the importance of the traditional accounts, it has long been recognized that limiting them to market transactions distorts them as a measure of economic activity and well-being. A vast and rapidly changing amount of nonmarket activity produces goods and services that are quite similar to those produced in the marketplace, but are omitted from traditional accounts. Time spent cooking hamburgers at Wendy's is counted in the national accounts, while cooking time at home is not; nannies' services are reckoned as part of GDP, while mommies' and daddies' services are not; the value of swimming in a commercial swimming pool is captured by GDP, while the value of swimming in a public lake or in the ocean is not.
In response to growing concerns about the accuracy of traditional measures of economic activity, many efforts have attempted to broaden the traditional accounts to include important sectors of nonmarket activity beyond the imputations of rent on owner-occupied housing, certain financial services, and the value of home-grown food, all of which were in the earlier accounts. The history of augmented accounting, some of which includes adjustments for the environment, goes back to the early 1970s (Eisner, 1971). Most of the early efforts were undertaken by private scholars. Significant examples of sectors examined in studies addressing extension of the accounts include household production and unpaid work, the services of consumer durables, research-and-development capital, leisure time, and informal and home education. In most countries, how-