If a colloquium on early entrepreneurs had been convened in the early 20th century, most participants would have viewed traders as operating on their own, bartering at prices that settled at a market equilibrium established spontaneously in response to fluctuating supply and demand. According to the Austrian economist Carl Menger, money emerged as individuals and merchants involved in barter came to prefer silver and copper as convenient means of payment, stores of value, and standards by which to measure other prices.