Back in May, John Authers wrote a column in the FT recommending that we change the frame when looking at market performance. For example, if we denominate the S&P 500 in sterling, euros and gold, the index has performed much more poorly over the last decade than it has in dollar terms.
Given all the market volatility in recent months, it's worth doing a similar analysis of how markets have performed since the March lows. Instead of gold, we'll use oil. Like other commodities, oil is being used as an inflation hedge. It also has significant intrinsic value, whereas gold has very little.

In dollar terms, the S&P 500 has gained significantly since it's bottom on 9 March. But currency fluctuations take a 15% edge off those same returns. In oil terms, equities show no change since bottom. Indeed, while equities and oil have followed different paths, oil and equities yield the same over that period.
While we're at it, there's another market phenomenon worth taking a look at. Most of the gains made in the history of equity investing in the DJIA have been made on just a few trading days. The CXOAG blog points out that the 10 best trading days in the history of the DJIA account for 65% of terminal wealth, while the 20 best trading days account for 83% of terminal wealth. (Just as importantly, avoiding the 10 worst trading days of the year would boost wealth by over 200%, but that's a separate analysis.)
Let's apply that thinking to the beginning of the equities rally. Suppose you didn't call a bottom on Friday the 6th, but instead jumped into the market on Wednesday the 12th.

We see that top-10-day phenomenon at work. Returns across the board are significantly lower, primarily due to changes in the index.
Currency fluctuations have a bigger impact on yield. Between 9 and 12 March, the S&P 500 jumped nearly 75 points. But market uncertainty kept demand high for US Treasurys. This kept the USD strong, and the exchange rate changed only from $1.2586 to $1.2719 during those few days. However, since then, the USD has slid considerably: from 12 March through today, the EUR-denominated investor is up on US equities, but not nearly as high.
More interesting is that the S&P has underperformed oil by 10%. If we think of oil as an inflation hedge, this is not a positive indicator.
As Mr. Authers pointed out in May, "Financial markets are not as efficient as many believed, but they can adjust swiftly when anomalies are exposed." Given the weakness of the dollar and the strength of commodities, US equity indexes framed in USD may not be telling a complete story. Restated, there may be significant market adjustments brewing in one dimension or another.