German beer is highly diverse and an important part of Germany's culture. There are around 1300 breweries in Germany, more than in any other country. The German beer market is a bit sheltered from the rest of the world beer market by the German brewers' adherence to the Bavarian Reinheitsgebot (purity requirement) dating from 1516, according to which the only allowed ingredients of beer are water, hops and barley-malt. Many breweries worldwide adopted the Reinheitsgebot for their own beers. After its discovery, yeast became the fourth legal ingredient, though for top-fermenting beers (ales) the use of sugar is also permitted. Through this law (which since 1988 has not applied to imported beer, but is still compulsory for German brewers), beers from Germany have a good reputation for their quality.