“The facts, indeed, connected with this gloomy department of statistics show that the most valuable period of human life—that in which a man is producing more than he is consuming—is that which provides the greatest number of victims.”

Source: The Limits of State Action (1792), Ch. 16

A Sense of the Mysterious : Science and the Human Spirit (2005), p. 200<!-- Pantheon Books isbn=0375423206 -->
Context: In the 1950s, academics forecast that as a result of new technology, by the year 2000 we could have a twenty-hour workweek. Such a development would be a beautiful example of technology at the service of the human being.... According to the Bureau of Statistics, the goods and services produced per hour of work in the United States has indeed more than doubled since 1950.... However, instead of reducing the workweek, the increased efficiencies and productivities have gone into increasing the salaries of workers.... Workers... rather have used their increased efficiencies and resulting increased disposable income to purchase more material goods.... Indeed, in a cruel irony, the workweek has actually lengthened.... More work is required to pay for more consumption, fueled by more production, in an endless, vicious circle.

1890s
Source: Candida, Act I (1898)

Source: The Light of Other Days (2000), Chapter 6

Source: The Way of All Flesh (1903), Ch. 66

The road back to Paris (1988)

Source: The circuit flow of money, 1922, p. 264

Source: Attributed in posthumous publications, Einstein and the Poet (1983), p. 103

also reported in the form: The peoples of the Balkans produce more history than they can consume, and the weight of their past lies oppressively on their present.
Although widely attributed to Winston Churchill (e.g. by the President of the British Academy, Professor Sir Adam Roberts), the quote is spurious.
The remark was quoted - although without attribution, and concerning East Central Europe instead - by Margaret Thatcher in her speech, "New Threats for Old," in Westminster College, Fulton, Mo., at a joint commemoration with the Churchill Centre of the "Iron Curtain" speech's 50th anniversary, on 9 March 1996: "It is, of course, often the case in foreign affairs that statesmen are dealing with problems for which there is no ready solution. They must manage them as best they can. That might be true of nuclear proliferation, but no such excuses can be made for the European Union's activities at the end of the Cold War. It faced a task so obvious and achievable as to count as an almost explicit duty laid down by History: namely, the speedy incorporation of the new Central European democracies--Poland, Hungary and what was then Czechoslovakia--within the EU's economic and political structures. Early entry into Europe was the wish of the new democracies; it would help to stabilize them politically and smooth their transition to market economies; and it would ratify the post-Cold War settlement in Europe. Given the stormy past of that region--the inhabitants are said to produce more history than they can consume locally--everyone should have wished to see it settled economically."
The sources of Thatcher's quote is likely a passage in the 1911 "Chronicles of Clovis", by Hector Hugh Munro (Saki), referring actually to Crete: "It was during the debate on the Foreign Office vote that Stringham made his great remark that "the people of Crete unfortunately make more history than they can consume locally." It was not brilliant, but it came in the middle of a dull speech, and the House was quite pleased with it. Old gentlemen with bad memories said it reminded them of Disraeli."
Misattributed
Source: Reinventing the Wheel http://www.gresham.ac.uk/lectures-and-events/reinventing-the-wheel-the-cost-of-neglecting-international-history. Footnote #5
Source: The speech is in James W. Muller, ed., Winston Churchill's "Iron Curtain" Speech Fifty Years Later (Columbia: University of Missouri Press, 1999), which collects the papers from that occasion. A readable .pdf is on the Churchill Centre website (scroll to pages 18-24): http://www.winstonchurchill.org/images/finesthour/Vol.01%20No.90.pdf
Source: Full text available here: https://en.wikisource.org/wiki/The_Chronicles_of_Clovis/The_Jesting_of_Arlington_Stringham