This paper examines the importance of year, industry, corporate-parent, and business-specific effects on the profitability of U.S. public corporations within specific 4-digit SIC categories. The results show that these factors account for 2%, 19%, 4%, and 32% of the aggregate variance in profitability, respectively. Industry effects account for a smaller portion of profit variance in manufacturing but a larger portion in lodging/entertainment, services, wholesale/retail trade, and transportation. The study finds a negative covariance between corporate-parent and industry effects. The analysis suggests that industry, corporate-parent, and business-specific effects are related in complex ways. The study uses comprehensive data and enhanced statistical methods to examine the relative effects of these influences on profitability for the economy as a whole and in broad economic sectors. Industry has a powerful direct and indirect influence on profitability. The study also finds that the influence of industry may be even stronger if data of finer grain were available. The study uses a model to estimate the effects of year, industry, corporate-parent, and segment-specific effects on profitability. The results show that industry effects account for nearly 19% of the variance in profitability, corporate-parent effects account for nearly 4%, and segment-specific effects account for nearly 32%. The study also finds that the results differ across economic sectors, with industry effects being more significant in some sectors than others. The study concludes that industry effects are an important determinant of profitability, and that the results are influenced by the data and methods used. The study also finds that the influence of industry may be even stronger if data of finer grain were available. The study uses a model to estimate the effects of year, industry, corporate-parent, and segment-specific effects on profitability. The results show that industry effects account for nearly 19% of the variance in profitability, corporate-parent effects account for nearly 4%, and segment-specific effects account for nearly 32%. The study also finds that the results differ across economic sectors, with industry effects being more significant in some sectors than others. The study concludes that industry effects are an important determinant of profitability, and that the results are influenced by the data and methods used.This paper examines the importance of year, industry, corporate-parent, and business-specific effects on the profitability of U.S. public corporations within specific 4-digit SIC categories. The results show that these factors account for 2%, 19%, 4%, and 32% of the aggregate variance in profitability, respectively. Industry effects account for a smaller portion of profit variance in manufacturing but a larger portion in lodging/entertainment, services, wholesale/retail trade, and transportation. The study finds a negative covariance between corporate-parent and industry effects. The analysis suggests that industry, corporate-parent, and business-specific effects are related in complex ways. The study uses comprehensive data and enhanced statistical methods to examine the relative effects of these influences on profitability for the economy as a whole and in broad economic sectors. Industry has a powerful direct and indirect influence on profitability. The study also finds that the influence of industry may be even stronger if data of finer grain were available. The study uses a model to estimate the effects of year, industry, corporate-parent, and segment-specific effects on profitability. The results show that industry effects account for nearly 19% of the variance in profitability, corporate-parent effects account for nearly 4%, and segment-specific effects account for nearly 32%. The study also finds that the results differ across economic sectors, with industry effects being more significant in some sectors than others. The study concludes that industry effects are an important determinant of profitability, and that the results are influenced by the data and methods used. The study also finds that the influence of industry may be even stronger if data of finer grain were available. The study uses a model to estimate the effects of year, industry, corporate-parent, and segment-specific effects on profitability. The results show that industry effects account for nearly 19% of the variance in profitability, corporate-parent effects account for nearly 4%, and segment-specific effects account for nearly 32%. The study also finds that the results differ across economic sectors, with industry effects being more significant in some sectors than others. The study concludes that industry effects are an important determinant of profitability, and that the results are influenced by the data and methods used.