S&P 500 soars past $15 trillion in value

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Of all the wild, standard-setting numbers that have come with this year's stock market rally, here's one that stands out: The S&P 500's total market value is now above $15 trillion.

The landmark breach came as the broad stock market index flirted with 1,700 in intraday trading, part of an 18.5 percent year-to-date rally.

Sparked by relatively dovish comments from Federal Reserve Chairman Ben Bernanke, some positive economic data and pledges for easier financial conditions in Europe, the S&P 500 passed its closing high of 1.682 in early Thursday trade.

(Read more: Cramer: I'm buying this stock right now)

The index's market value is now about $15.02 trillion, according to Howard Silverblatt, senior index analyst at S&P Dow Jones Indices.

In the current bull market, the S&P 500 has gained $9.1 trillion in value. That compares to the $7.9 trillion it lost during the bear market of 2007-09 and $5.8 trillion in the previous bear run from 2000-02.

One other hopeful number Silverblatt pointed out: The total stock market value could nearly pay off the national debt of $16.7 trillion.

(Read more: Bernanke: Fed to taper but will be flexible)

"While market value is not the same as price level, the changes do tell a story," he said.

The Dow Jones industrials also hit a fresh high, crossing 15,542.

Despite all the big numbers, Wall Street remains cautious on the market.

Analysts on average are recommending investors allocate just less than half—49.8 percent—to stocks in their portfolios, only a shade above the 47 percent level at the end of 2012, according to Bank of America Merrill Lynch.

(Read more: $1 in market in 2000, today would be...$1)

That, according to the firm, is a contrary indication that the $15 trillion number could continue.

"Against this skeptical backdrop," said BofA analyst Savita Subramanian, "the bull market in equities may still have room to run."

By CNBC's Jeff Cox. Follow him @JeffCoxCNBCcom on Twitter.