One of the biggest areas of controversy over CAPEs or cyclically adjusted price/earnings multiples (see this earlier post and the huge correspondence it provoked) concerns exactly how earnings are measured, and how they can be compared over time. Neither is a unique problem for CAPE compared with other valuation metrics, but they can still change conclusions over the vital topic of whether the US stock market is now overpriced.
There is action on this front in the academic world, with Jeremy Siegel of the Wharton School proposing that an alternative measure of earnings should be used. This might change conclusions, and there will be more on that next week. For now, I would like to introduce another fascinating attempt to alter the methodology of Yale’s Robert Shiller, who has been central to popularising the CAPE over the last two decades.
Back in 2009, Alain Bokobza of Societe General released the results of his own new normalised CAPE, and his colleagues have kindly updated his data. The essential new insight was that corporate taxation has not been constant over the years. Rather, it was introduced in 1911 at only 1.5 per cent. After the First World War it rose to 15 per cent, and then, as the apparatus of the welfare state rolled out over the ensuing decades, it rose to 40 per cent. Mr Bokobza contends that this affects the multiple that investors will pay. So he recalculated the CAPE for the years before 1950, assuming a 40 per cent tax rate.
To give a quick example; If you pay $100 for $10 of earnings untaxed, you have paid a p/e of 10. If it is taxed at 40 per cent, you have paid a multiple a little above 16 on post-tax earnings. This comparison may more accurately, according to Mr Bokobza, help build a norm for what investors are prepared to pay for the earnings they buy. Without making such an adjustment, Mr Bokobza contends, we are effectively comparing post-tax earnings post-war with what can almost be called pre-tax earnings pre-war. This is a contentious point of view; throughout the period, taxation was a given for investors. Many other factors were also changing. But it makes a case that pre-war multiples may not be directly comparable to post-war ones, and suggests an intuitive fix. (And indeed the comparability of earnings is the subject of growing academic debate, and is very relevant when trying to get a handle on long-run valuations). A look at how this changes the historical picture comes after the break. Read more