The process of turning milk into cheese involves using an enzyme called chymosin. Traditionally in the West, chymosin was obtained from rennet, a substance extracted from the stomachs of dead baby cows. This is obviously problematic from a vegetarian point of view, but thankfully in America and the U.K. at least, companies have mostly have mostly stopped using rennet; instead they mostly produce chymosin through fermentation. Here's what Wikipedia says:
FPC [Fermentation-produced chymosin] was the first artificially produced enzyme to be registered and allowed by the US Food and Drug Administration. In 1999, about 60% of US hard cheeses were made with FPC, and it has up to 80% of the global market share for rennet. By 2008, about 80% to 90% of commercially made cheeses in the US and Britain were made using FPC.
My question is, how do you distinguish between the 80-90% of cheeses that don't use rennet, vs. the 10-20% of cheeses that do? Is there something to look for in the labeling?