Vintage Vs. Non-vintage
The majority of the Champagne produced is non-vintage (also known as mixed vintage or multivintage), a blend of wines from several years. This means that no declared year will be displayed on the bottle label. Typically, however, the majority of the wine is from the current year but a percentage is made of reserve wine from previous years. This serves to smooth out some of the vintage variations caused by the marginal growing climate of Champagne, which is the most northerly winegrowing region in France. Most Champagne houses strive for a consistent house style from year to year (largely for reasons related to price-setting and successful marketing), and this is arguably one of the hardest tasks of the house winemaker.
The grapes to produce vintage Champagne must be 100% from the year indicated (some other wines in the EU need only be 85% to be called vintage, depending on their type and appellation). To maintain the quality of non-vintage Champagne a maximum of half the grapes harvested in one year can be used in the production of vintage Champagne ensuring at least 50%, though usually more, is reserved for non-vintage wines. Vintage Champagnes are the product of a single high-quality year, and bottles from prestigious makers can be rare and expensive.
Read more about this topic: Sparkling Wine Production