"In 1913, the average personal income was $621. Only 2 percent of the population was liable for the [income] tax between 1913 and 1915. Eighty percent of the returns were filed by people involved in business; 17 percent were in the professions, 3.3 percent in agriculture, and 0.5 percent were laborers. Businessmen reported 85 percent of the income and paid almost 90 percent of the revenues.
Given the level of incomes in those days, it was a tax aimed strictly at the richest people in the country. If the system were in place today, a single person making less than about $65,000* would pay no tax. A couple earning less than $86,000* would pay nothing. Incomes up to $430,000* would be in the 1 percent bracket. Someone would have to make $11 million* before paying the top 7 percent rate. In  dollars, the exemptions of 1913 would be worth $65,000* for single people and $86,000* for married couples."