Interest rates sure are weird these days. Five central banks currently hold policy rates negative; several are dabbling with unconventional bond-buying. The one bank that tried to raise them, the Federal Reserve, found itself back cutting rates within a year. Meanwhile, some $11 trillion worth of bonds have negative rates—guaranteeing losses for buyers that hold those to maturity.

But however weird this moment might be, it’s also entirely predictable—with the benefit of 700 years of hindsight, that is.

That insight comes courtesy of a fascinating working paper by economist Paul Schmelzing, which reconstructs real interest rates in advanced economies dating back to 1311. The study—what the author says is the first construction of a dataset of high-frequency GDP-weighted real rates (i.e. the difference between the nominal yield and inflation)—features a staggeringly rich collection of records culled from diaries, account books, local archives, and municipal registers and includes everything from Medici bank loans to France’s “Revolutionary loans” to the US government.