The great sage and baseball legend, Yogi Berra, once said:

“It’s tough to make predictions – especially about the future.”

But financial planning is all about contemplating how much money will result from a particular savings rate combined with an assumed rate of return. It’s also about arriving at a reasonable spending rate given an amount of money and an assumed rate of return. In other words, plugging in a rate of return is unavoidable when doing financial planning. Perhaps financial planners should use a range of assumptions, but some assumption must be made.

The good news is that bond returns stand in defiance to Berra’s dictum; they aren’t too difficult to forecast. For high-quality bonds, returns are basically close to the yield-to-maturity. Stock returns are harder, but there are ways to make a decent estimate. The Shiller PE has a good record of forecasting future 10-year stock returns. It’s not perfect; low starting valuations can sometimes lead to low returns and vice versa. But it does a decent job. And the further away the metric gets from its long-term average in one direction or another, the more confident one can be that future returns will be abnormally high or low depending on the direction in which it has veered from its average. Currently, the Shiller PE of US stocks is over 30, and its long-term average is under 17. That means it’s unlikely that future returns will be robust.

The following graph shows end-of-April return expectations for various asset classes released by Newport Beach, CA-based Research Affiliates. One will almost certainly have to venture overseas to capture higher returns. And those likely posed for the highest returns – emerging markets stocks – come with an extra dose of volatility. Along the way, there will be problems caused by foreign currency exposure too, though Research Affiliates thinks foreign currency exposure will likely deliver some return.

Hope for a correction? Move some money to cash?

Given this return forecast, investors will have to contemplate saving more and working longer. But investors who continue to save should also hope for a market downturn. As perverse as that sounds, we are in a low-future-return environment because returns have been so good lately. We have basically eaten all the future returns over the past few years. And nothing will set up financial markets to deliver robust returns again like a correction. That’s why the Boston-based firm Grantham, Mayo, van Otterloo (GMO), which views the world similarly, though perhaps a bit more pessimistically, to Research Affiliates has said that securities prices staying at high levels represents “hell,” while a correction would represent investment “purgatory.” If prices stay high, and there are no deep corrections or bear markets, there will be little opportunity to invest capital at high rates of return for a very long time.

Investors who aren’t saving anymore should hold some extra cash in anticipation of purgatory. If we get purgatory (a correction) instead of hell (consistently high prices without correction), the cash will allow you to invest at lower prices and higher prospective return. How much extra cash? Consider around 202%. The Wells Fargo Absolute Return fund (WARAX) is run by GMO, and 81% of its assets are in the GMO Implementation fund (GIMFX). Around 6% of the Implementation fund is in cash and another 16% of the fund is in U.S. Treasuries with maturities of 1-3 years, according to Morningstar. So more than 20% of the Implementation fund – and nearly 20% of the Absolute Return fund — is in Treasuries of 3 years or less or cash.

Around 52% of the Implementation fund is in stocks, most of them foreign stocks. So around 40% of the Absolute Return fund is in stocks. (The other holdings of the Absolute Return fund are not invested in stocks as far as I can tell.)

If you normally have something like a balanced portfolio with 50% or 60% stock exposure, it’s fine to take that exposure down to 40% right now. There is no question that this is a hard game to play. The cheaper prices you’re waiting for as you sit in short-term Treasuries or cash, with roughly one-third of your money that would otherwise be in stocks, may not materialize. After all, as Berra said, “It’s tough to make predictions.” Or the lower prices may materialize only after your patience has expired, and you’ve bought back into stocks at higher prices just before they’re poised to drop.

These adverse outcomes are real possibilities. But the buy-and-hold, strictly balanced allocation (60% stocks/ 40% bonds) also isn’t easy now for those who (legitimately) fear a 30+ Shiller PE. That’s why it’s arguably reasonable to move some of your stock allocation into cash and/or short-term Treasuries, but not the whole thing. And sitting in cash hasn’t been this easy for a decade or more, now that money markets are yielding over 1% and instruments like PIMCO’s Enhanced Short Maturity Active ETF (MINT) are yielding over 2%. Those yields at least act as a little bit of air conditioning if investment hell persists and prices never correct while you sit in cash with some of your capital.