Has the underground economy caused the increase in United States GNP in recent years to be understated relative to earlier periods? The ratio of employment to population provides powerful evidence that it has not. This ratio’ was as high in the middle 1970s as in previous periods and in 1978–80 rose to its highest level of the postwar era, suggesting that employment growth has not been understated. Employment series based on both establishment reports and household surveys yield exceptionally high ratios in recent years. This article provides a step‐by‐step explanation of why employment data are pertinent to the question raised about GNP.This explanation may be summarized as follows. GNP measured as the sum of final products is not understated unless GNP measured as the sum of national income and other charges against GNP is also understated. Appreciable understatement of the growth of charges against GNP as a result of growth of the underground economy is highly unlikely in the absence of understatement of the growth of wages and salaries, because of the way the estimates are made. Understatement of the growth of wages and salaries without understatement of the growth of employment based on establishment reports is highly unlikely because of the way data are collected.The article explains briefly the relationship between income tax evasion and errors in measuring the various components of charges against GNP. It also explains how illegal activities are meant to be handled in GNP meas