Ed Glaeser at the NYT on efficiencies in government:
Before the 20th century, even the best governments had difficulty accurately assessing private financial wealth and income. Governments taxed more measurable things, like imports, real estate and even windows. A window tax may seem silly, but windows are awfully easy for a tax collector to see. As economies moved from informal agriculture to well-recorded industry, broad taxes on income and wealth became easier to put in place and the size of the government grew enormously.