It's important to note that US performance is exceptional relative to that of other countries. Part of the risk in the equity risk premium is that we might eventually regress to the mean.
Another underappreciated point is that it was during the most recent period of data that we abandoned hard currency (left the gold standard). It wasn't widely understood that inflation is a threat to bonds but less so to equities (corporations can pass inflation through to consumers -- costs, revenue and earnings are all in real dollars).
Economist: Contrary to popular belief, stocks do not always go up
IF AMERICAN investors have learned any lesson in the last 25 years, it is to buy shares on the dips. The slide in 2000-02 may have been longer and deeper than they were used to but normal service was eventually resumed, driving the Dow Jones Industrial Average to a record high on October 1st.
Among American financial commentators, it is almost universally accepted that shares always rise over the long run. And this perception does seem to be backed up by evidence; if you take any 20-year period, Wall Street has always delivered positive real returns. In addition, one ought to expect shares (which are risky) to deliver a higher return than risk-free assets such as government bonds.
...Elroy Dimson, Paul Marsh and Mike Staunton of the London Business School examined* the record of 16 stockmarkets which were in continuous operation over the course of the 20th century. In itself, this selection showed survivorship bias by excluding the likes of Russia and China. The academics found that only three other countries could match the American record of having no 20-year periods with negative real returns.
Other investors were far less lucky. Japanese, French, German and Spanish investors all suffered instances where they had to wait 50-60 years to earn a positive real return; in Italy and Belgium, the waiting period stretched to 70 years. It was no good following the famous advice to “put the shares in a drawer and forget about them”; the furniture would not have lasted that long.
Besides survivorship bias, there is another problem with the belief that stockmarkets must always go up; the very existence of the belief is likely to lead to its falsification. Investors will keep buying until prices reach stratospheric levels. That clearly happened in Japan in the late 1980s and with the technology-heavy NASDAQ index in the late 1990s; the latter is still, after seven years, not much more than half its peak level.
A significant proportion of the return from equities in the second half of the 20th century came from a re-rating of shares; investors were willing to pay a higher multiple for profits. But re-rating cannot continue forever. Although ratings have fallen significantly since the heady days of 2000, that is in large part due to the remarkable strength of corporate profits, now close to a 40-year high relative to national output. If profits revert to the mean, that could act as a drag on stockmarket performance. And, as with Japan, investors do not have much in the way of income to fall back on; the dividend yield on the American market is just 1.7%.
If investors want a simple parallel with share prices, they need only turn to the American housing market. Back in 2005, Ben Bernanke, then an economic adviser to the president, was asked about the possibility of a decline in house prices on CNBC, a financial-television channel. He said, “We've never had a decline in housing prices on a nationwide basis. What I think is more likely is that house prices will slow, maybe stabilise.”
Lots of people took the same view and were willing to borrow (and lend) on a vast scale on the grounds that higher house prices would always bail them out. They are now counting their losses. Investors in equities should beware of overcommitting themselves on the basis of a similar belief. Just ask the Japanese.