The most persistent bullish argument I have heard is that the rally will not end until investors start putting money into stock mutual funds. Bulls point to the lack of inflows into mutual funds as proof that the rally has not been embraced. However, I believe that mutual funds are losing their importance as more investors either invest themselves or through ETFs.
I recently read that ETF assets grew by $50 billion in March. I believe this low cost way of investing is now preferred to high cost mutual funds. Many would counter that bond mutual funds are still seeing massive inflows. I would point out that the bond market is a dealer market that only institutions and large investors can deal in. In the case of the bond market, if one wants an allocation there are few ways to get around the fees.