Why is a fractional reserve banking system neccessary?

Answer 1

When fractional reserve banking was first established (hundreds of years ago), it was used as a buffer against bank runs, or events when the general public flocks to the banks and withdraws all of their cash. When this happens, the banks have no more capital to lend and therefore go bankrupt. Nowadays, another use is utilized by the Federal Reserve. When banks have a reserve requirement, they keep a certain amount of money with them, not necessarily for the sake of funding bank runs, for this is not as much of an issue now that the FDIC insures all deposits, but for what is called the multiplier effect. The multiplier is an economic tool used by the Fed in times that call for monetary policy. Long story short, it allows money that is injected into M1 (the general money supply) by the Fed to expand and have a greater impact on interest rates, which in turn effect savings/investment and aggregate demand at large. Keeping more in reserve (raising the reserve ratio) would lower the multiplier effect and thus reduce the Fed's control over the economy in times of economic crisis, like the most recent recession. Conversely, keeping reserves high would increase the multiplier effect and allow the Fed to react more effectively in changing interest rates as well as short run equilibrium of aggregate demand and supply of the economy.