Sushi originated in Japan as vinegared rice stuffed with raw fish like tuna. As tuna demand increased, Japan began sourcing it from other countries. Sushi was initially difficult to introduce in Western cultures who were uneasy with raw fish consumption, but it gained acceptance as a sign of class through Japanese cooking classes for women that omitted raw fish, and the opening of sushi bars in places like New York's Harvard Club. The global popularity of sushi led to Japan's tuna market expanding to other countries to meet demand, while Japanese workers were seen as more skilled at preparing sushi outside Japan due to their expertise in handling tuna.