Proprietary trading (also "prop trading") occurs when a trader trades stocks, bonds, currencies, commodities, their derivatives, or other financial instruments with the firm's own money, aka the nostro account, contrary to depositors' money, in order to make a profit for itself. Proprietary traders may use a variety of strategies such as index arbitrage, statistical arbitrage, merger arbitrage, fundamental analysis, volatility arbitrage, or global macro trading, much like a hedge fund. Many reporters and analysts believe that large banks purposely leave ambiguous the proportion of proprietary versus non-proprietary trading, because it is felt that proprietary trading is riskier and results in more volatile profits.