A 50 year-long business cycle, named after Nikolai Kondratieff, a Russian economist. He claimed to have identified cycles of economic activity lasting half a century or more in his 1925 book, The Long Waves in Economic Life. Because this implied that capitalism was, ultimately, a stable system, in contrast to the Marxist view that it was self-destructively unstable, he ended up in one of Stalin’s prisons, where he died. Alas, there is little hard evidence to support Kondratieff’s conclusion.