Definition - What does Yield mean?
Yield is the measurement pertaining to the quantity of grapes at harvest time. In Europe, this is measured in hectoliters per hectare. In the Americas, it is measured in tons per acre.
In the Old World it is not uncommon for there to be a standard maximum allowable yield per hectare regulated according to the wine region. Yields produced will determine how a wine is ranked and labeled.
WineFrog explains Yield
In many wine-making regions, it is believed that lower yields produce better quality wines. This is not always the case, as it also depends on the soils in which the grapes are grown, vineyard management and variety of wine grape.
Throughout many wine-making regions in Europe, it is not uncommon for wine laws to regulate how much a vineyard can harvest per hectare.
In France, varying wine regions have regulations based on the classification of their wines in accordance with yield restrictions. Crus, for instance have strict regulations on how much juice they can make per hectare. In Germany, a wine is labeled depending on the yield harvested and the amount of sugar in the grapes must (juice). Spain, Italy and other reputed wine countries also have restrictions on yields produced at harvest according to labelling laws.