Email last week brought a copy of The Gypsy Economist: The Life and Times of Colin Clark, by Alex Millmow. Starting in the 1930s, Clark (1905-1989) was an important student of global economic development who, though born in London, spent most of his career in Australia. The same mail brought news, too, of the death of international macroeconomist Robert Mundell. He was 88, a Canadian who spent 45 years at Columbia University. Another decade or two will pass before an even-handed biography of Mundell arrives, but it will be worth the wait. Mundell was a brilliant student of the rapid…