“While the economy has come a long way toward achieving better balance and reaching our 2 percent inflation goal, we are not there yet.”“I am committed to fully restoring price stability in the context of a strong economy and labor market.”“As we navigate the remainder of this journey, I will be focused on the data, the economic outlook, and the risks, in evaluating the appropriate path for monetary policy that best achieves our goals.”
"But as long as stocks and bonds have a negative correlation, we can at last reduce this higher volatility in a mixed stock/bond portfolio. And bonds have a negative correlation with stocks, don’t they? Don’t they? …please tell me that stocks and bonds have a negative correlation in the long run because that is the foundation of stock/bond portfolios recommended by asset managers and banks everywhere.
Since the 1960s, the correlation between stocks and bonds has been either very low or even negative. This is the time when modern portfolio theory was born and when stock/bond portfolios became the workhorse benchmark against which to assess all other investment approaches.
But before the 1960s, the correlation between stocks and bonds was on average 0.5 to 0.6, much higher than any investor today expects it to be going forward. If the correlation between stocks and bonds is that high, the diversification benefits from investing in stocks and bonds are much smaller as these two asset classes increasingly move in lockstep.
Note that even since the 1960s there have been large swings in the 20-year correlation between the two asset classes. Notably, in the 1970s the correlation increased, before falling again in the 1990s.
Concluding that basically the fundamental premise of asset allocations could be questionable:
Depending on the regime you expect and the assumptions on correlation you make, the allocation to stocks and bonds will be very different going forward. In a world of high correlation between stocks and bonds, the allocation to bonds will likely be smaller, unless you also expect the equity risk premium to be smaller (which again depends on your expectations for growth, inflation, etc.). In a world of negative correlation between stocks and bonds, the allocation to bonds will be higher, unless you expect the equity risk premium to be larger.
Klement's writing reminded me of an article that turned into a book by Seb Page of T. Rowe Price called When Diversification Fails. In the article Page cites research showing the following:
Based on a precrisis data sample ending in February 2008, Chua, Kritzman, and Page (2009) documented significant “undesirable correlation asymmetries” for a broad range of asset classes. Not only did correlations increase on the downside, but they also significantly decreased on the upside. This asymmetry is the opposite of what investors want. Indeed, who wants diversification on the upside? Upside unification (or antidiversification) would be preferable.
Page's article focuses mainly on how diversification fails most notably at times when investors need it most, especially during crashes (i.e. "left-tail events"). His article shows that hedge funds and private assets do little to solve the diversification problem. Ultimately the article provides:
Unexpected changes to the discount rate or inflation expectations can push the stock–bond correlation into positive territory—especially when other conditions remain constant.
"In an apocryphal story, a statistician who had his head in the oven and his feet in the freezer exclaimed, “On average, I feel great!” Similarly, as a measure of diversification, the full-sample correlation is an aver-age of extremes. Conditional correlations reveal that during market crises, diversification across risk assets almost completely disappears. Moreover, diversification seems to work remarkably well when investors do not need it—during market rallies. This undesirable asymmetry is pervasive across markets. Our findings are not new, but we proposed a robust approach to measure left- and right-tail correlations, and we documented the extent of the failure of diversification on a large dataset of asset classes and risk factors. The good news is that tail risk– aware analytics, as well as hedging and dynamic strategies, are now widely available to help investors manage the failure of diversification."