OPINION LETTERS

摘要

Like many readers, I'm sure, I read the article on the decline of phytoplankton and the cost of carbon fixes with a sense of dread (7 April, p 42). It reminded me of historian Paul Kennedy's theory of imperial overstretch. In his 1987 book The Rise and Fall of the Great Powers, this Yale professor of economic history demonstrated that empires tend to expand until (basically) the amount that can be raised in taxes is lower than the cost of enforcing taxation, and the economy collapses.