Ariyalur for investment expenditure: the sum of all private expenditures on capital goods like buildings, equipment, and machinery. labor force: all civilian persons, typically over the age of sixteen, who are employed or actively seeking employment. labor income: the wages or salaries received by laborers in exchange for supplying a specific amount of labor. labor union: a group who joins together on behalf of certain laborers in order to maximize the collective ben- 940 Glossary efit of those laborers regarding their wages, fringe benefits, work conditions, etc. Laffer curve: a graphical bell-shaped relationship between (income) tax rates and tax revenues. When the tax rate is zero, and when the rate is one hundred percent, government receives no tax revenues. However, as tax rates are adjusted away from these extremes, tax revenues rise to a maximum point somewhere in between. Ariyalur 2016.