adam smith basic income composite good comprehensive income consumer theory depreciation dividend earnings per share economics ffo financial statements gini coefficient haig-simons income income inequality metrics income statement income tax income trust interest international accounting standards board lorenz curve measures of national income and output net national income nicholas barr passive income per capita per capita income permanent income hypothesis private income pro forma profit public company real estate real estate investment trust remuneration retained earnings revenue stock and flow tooth fairy united states warren buffett wiktionary windfall gain