Due to the financials crisis and the ensuing policies of central banks around the world, there have been a lot of relationships in the financial markets over the last few years that have deviated from their long-term historical norms. One of those concerned the relationship between equities and crude oil. For decades, the correlation between equities and crude oil prices fluctuated between positive and negative territory. A funny thing happened in late 2008, though, when the correlation between crude oil and the S&P 500 moved into positive territory and stayed there.
As shown in the chart below, from October 2008 through last week, the rolling 200-day correlation between the closing prices of the S&P 500 and crude oil never once moved into negative territory. That streak of 1,327 trading days was the longest stretch where equities and crude oil were positively correlated since at least 1980. To put that streak into perspective, the second longest stretch of positive correlation between the two asset classes was only 414 trading days from early 1987 through July 1988. A lot of aspects of the financial markets were thrown off kilter during the financial crisis, so let's just hope that the ending of positive correlation between these two asset classes is a sign of a return to normalcy in the financial markets.