By vintage

Wines may be classified by the year in which the grapes are harvested, known as the "vintage". "Vintage wines" are made from grapes of a single year’s harvest, and are accordingly dated. Some wines can improve in flavor as they age, and wine enthusiasts will occasionally save bottles of an especially good vintage wine for future consumption.

Most countries allow a vintage wine to include a portion of wine that is not from the labeled vintage. In Chile and South Africa, the requirement is 75 percent. In Australia, New Zealand, and the member states of the European Union the requirement is 85 percent. In the United States the requirement is 95 percent same-year content for vintage-dated wine. In theory, the 95 percent rule in the United States applies equally to foreign imports, but there are obvious challenges in enforcing the regulation.

For some types of wine, the best-quality grapes and the most care in wine-making are employed on vintage wines and they are therefore more expensive than non-vintage wines. Whilst vintage wines are generally made in a single batch so that each and every bottle will have a similar taste, climatic factors can have a dramatic impact on the character of a wine to the extent that different vintages from the same vineyard can vary dramatically in flavor and quality. Thus, vintage wines are produced to be individually characteristic of the vintage and to serve as the flagship wines of the producer. Non-vintage wines, however, are blended from a number of vintages for consistency, this allows wine makers to keep a reliable market image and also maintain sales even in bad vintage years.

Superior vintages, from reputable producers and regions, will often fetch much higher prices than their average vintages. Some vintage wines are only made in better-than-average years. Conversely, wines such as White Zinfandel, which do not age well, are made to be drunk immediately and may not be labeled with a vintage year, though there are exceptions. French Champagne is often non-vintage, but still expensive. It can sometimes profit from aging 2-3 years and some Prestige Cuvées even much longer.

There is some disagreement and research [9] about the significance of vintage year to wine quality.