It depends on how they saved it. If people put it under their mattress it would be a problem. If they keep it in a bank (which offers an interest rate) the bank

It depends on how they saved it. If people put it under their mattress it would be a problem. If they keep it in a bank (which offers an interest rate) the bank can loan that money out again, which massively increases the money supply. The stock market is a far smaller market compared to credit and loan markets.