The Federal Reserve and other central banks manipulate interest rates every day, James Grant of Grantās Interest Rate Observer told CNBCās āClosing Bellā on Thursday. āThe Fed is in the business of trying to manipulate markets, the macro economy, interest rates, unemployment and inflation through various monetary means, including the twisting around of yield curves and interest rates,ā Grant said. Grant added, āThe Federal Reserve fixes rates on principle. They have āoperation twistā that manipulates the credit markets. They have quantitative easing that manipulates bond yields.ā