The S&P 500 closed at a new all-time high on Tuesday and has rallied by around 52% since hitting its low point on March 23 — the best run the index has ever had in such a short time.

The state of play: While the market has continued to rise for the past five months, most investors have been incredulous about the sustainability of gains.

What's happening:Data from the Investment Company Institute show equity funds continue to see outflows and bond funds continue to see inflows.

• For the week ended Aug. 5, the last week for which data are available, investors pulled $20.3 billion out of equities and put $27.3 billion into bonds.
• Equity funds have seen net outflows in every month this year and they have increased in recent months as stock prices have gone up — outflows in March, when the market crashed to its nadir were $25.6 billion, but rose to $45.1 billion in June and totaled $76.7 billion in July based on ICI weekly estimates.

Money market funds, which are ostensibly savings accounts, also have been stubbornly high in 2020 despite the booming market.

• Investors have parked at least $4.5 trillion of cash in money markets since the week ending April 15.
• That's about 50% more — $1.5 trillion — than MMFs held in April 2019 and an increase of more than $600 billion from the highest level of holdings following the global financial crisis.

What they're saying: "The S&P 500 has been impressive and has created a lot of wealth, but I am not sure that reflects the overall health of the economy," Patrick Leary, chief market strategist at Incapital, told Reuters.

• "The rally has more to do with asset inflation, which is fueled by all the liquidity and all the continued support in the economy as well as the weakening dollar."

Yes, but: Some asset managers are starting to get bullish in public and in notes to their clients, encouraging stock buying.

Watch this space: Divergence continues to be a major theme in the stock market. Big U.S. tech stocks have led the way, with the Nasdaq up 22% year to date, setting new record highs for months.

• U.S. equities continue to outperform the rest of the world with MSCI's index of global stocks excluding the U.S. down 4.7% year to date, compared to the S&P's 4.9% gain.