After enduring a deep stock market correction in late 2018, investors quickly bought up stocks. And the bull market resumed.

It’s been a decade since the financial crisis lows, and two decades since the 1999 stock market blow-off bubble top. In today’s chart, we put our party hats on as we look at an interesting stock market ratio; The S&P 500 / NYSE Ratio

As you can see in the chart below, this ratio is testing the highs that it made in 1999.

This comes at a time when the market is still trying to confirm a broader breakout to new highs. While the Nasdaq and S&P 500 are at all-time highs, the Dow Industrials and Russell 2000 are not.

Will this ratio top out here? Or will it break out to new highs? The outcome may determine how long the party lasts.