A working paper published by the Federal Reserve on September 4 examines the extent to which the Fed's asset purchase programmes have contributed to a drop in Treasury yields. The authors weigh the timing of the introduction of the programmes against market expectations of the Fed's balance sheet and interest rates.

Since the inception of the first asset purchase programme in 2008, the authors say the yield on 10-year Treasuries has contracted by 160 basis points. They estimate that, as of June