Investors are an emotional crowd, especially when US equities, measured by either the Dow Jones Industrial Average or the more accurate S&P 500 index, have just hit all-time highs. I am not sure who first remarked that market behaviour is motivated by two competing emotions, fear and greed. But I do know that Albert Einstein claimed that “Three great forces rule the world: stupidity, fear and greed”.

Some of the macroeconomists that I have learned not to ignore, like Lawrence Summers and Martin Wolf believe that the outlook for the US economy under President Trump is at best uncertain, and that the recent equity market highs are a “sugar rush”. I recognise that some of these critics have major political differences with the new Administration. But many others, like the perceptive and apolitical John Authers, are also very concerned about equity over-valuation.

So, are investors being “stupid”?

One of the advantages of using economic models to analyse the equity market is that the models should be good at avoiding all three of Einstein’s great forces.

That does not make the models the only source of wisdom about future asset returns. Far from it. They are good at avoiding some of the behavioural mistakes that investors are known to commit, such as a tendency to dislike losses about twice as much as they like gains. But human beings may be better at recognising when the investment climate is about to change because of policy upheavals.

In this article, I will try to eliminate emotion by reporting some recent results from the suite of economic and financial models built by Juan Antolin Diaz and his team at Fulcrum. The results are somewhat encouraging: recession risks in the US are low and the over-valuation of equities is less clear cut (on some measures) than is sometimes supposed.

In the short term, however, there are signs that the most active short term traders in the market may be heavily exposed to equities at the present time. This could make the market vulnerable in the short term to policy shocks that cannot be incorporated into the models, such as a major outbreak of trade protectionism. Read more

The recent buoyancy in global equities has raised fears that the markets have entered a major bubble, driven by the unprecedented expansion in central bank balance sheets.

To the extent central bank asset purchases have reduced government bond yields, they have certainly brought forward returns from the future into the present, thus reducing expected returns on both equities and bonds. But this is normal in a period of monetary easing, and it does not automatically mean that markets are in a bubble. Read more

Global equities have, so far, survived the bout of global deleveraging which followed Ben Bernanke’s remarks about slowing the pace of QE last month, though there have been nasty signs of volatility in Japanese and some emerging markets. Investors have, unsurprisingly, become temporarily obsessed by whether the Fed will taper its asset purchases in September or December. However, in the great scheme of asset valuation, this is nothing more than a passing detail. In the longer term, what matters is real factors, like the forward path for corporate earnings, and the interest rate at which they should be discounted.

The appropriate discount rate is the risk-free (real) bond yield plus the equity risk premium (ERP). The Fed acts on the former, while the market determines the latter. In recent years, the Fed has reduced the bond yield but the market has, simultaneously, required a higher ERP, so the overall discount rate on equities has remained broadly unchanged. As I have argued before, any rise in the bond yield as QE ends may be offset by a fall in the ERP, leaving the valuation of equities protected as bond returns become negative. We have seen a minuscule version of this playing out in recent weeks, for what it is worth.

This, however, does not necessarily mean that equities are fairly valued. A common concern among investors is that the profit share in the US economy is currently abnormally high, which is one reason why US equities have performed so well since 2009. It is frequently argued that the profit share must eventually “mean revert”, and when that happens the market will have to revise downwards its estimates of the sustainable path for corporate earnings. Equities will tumble, not because of a hostile Fed, but because the fundamental earning capacity of corporate America will be found wanting.

This, however, seems to underplay the persistence and global breadth of the rise in the profit share, and the accompanying decline in the wage share, in the last three decades. It is far from clear why this trend should “mean revert” in the foreseeable future. Read more