In Chronique (souvent) Bordelaise you can read about the evolution of harvest yields in Champagne. When the appellation was created in 1935 the maximum yield was defined as 7500 kg/hectare. (In Champagne they count in kg/ha instead of the measure hectolitres/ha used in most other districts. 7500 kg/ha corresponds to approx 50 hl/ha.)
By 1998 they maximum yield had reached 8500 kg/ha (ca 57 hl/ha).
Today the allowed harvest volume is (after the latest increase earlier this year) 15,500 kg/ha (ca 103 hl/ha).
A curious contrast to most other regions that make efforts to restrict yields to increase quality.
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