In most of the New World, yield is measured in tonnes per hectare (or short tons per acre in the USA) – i.e. by mass of grapes produced per unit area.
Somewhere around 50 hectoliters per hectare, or 3 tons per acre, is a typical representative figure for many countries and regions.
One school of thought, generally subscribed to in France, claims that great red wine is impossible to produce at yields exceeding 50 hl/ha.
Another school of thought claims that a yield of 100 hl/ha is possible to combine with high quality, provided that careful canopy management is used.
[1][7] In both France and Italy, the maximum allowed yields are regulated in wine laws, and vary between appellations.