For 200 years, interest rates rose when prices rose — the opposite of theory

Under the gold standard, interest rates and the general price level moved together for roughly two centuries, even though standard theory says they should move oppositely as inflation erodes real returns. Banker Alfred Herbert Gibson spotted the pattern in 1923; Keynes found it so strange he called it 'one of the most completely established empirical facts in the whole field of quantitative economics.'

— John Maynard Keynes, A Treatise on Money — Volume 2, 1930; correlation first noted by Alfred Herbert Gibson, Banker's Magazine, 1923
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