The stock market is only 50% through its current bull rally based on historical average, NDR says

• The current bull market in stocks is only halfway through its average length, according to Ned Davis Research.
• And when considering the average length of secular bull markets, the current rally could last another few years.
• "The length of the current rally is not extreme," Ned Davis Research said.

The current bull market in stocks is only 344 trading days old, suggesting that stocks could continue to rise for the foreseeable future, according to a Wednesday note from Ned Davis Research.

The average length of a bull market is 694 trading days, implying that the current rally in stocks is only at the halfway mark, based on history, according to NDR.

The firm created a sentiment chart that measures the length of time the S&P 500 goes without a 20% decline, which is the most commonly cited threshold for stocks to be considered in a bear market.

"A quick look at the size of the triangles on these correction charts lets me know if the current run for an index is getting 'long in the tooth,' relative to history," NDR senior portfolio strategist Pat Tschosik said. "A quick look at the current case for the S&P 500 shows a relatively small triangle, giving comfort that the length of the current rally is not extreme."

The outlook gets even more bullish when investors consider the average length of a secular bull market, which NDR believes the stock market is in. Secular bull markets on average last 1,105 days, suggesting that the current bull rally is only 30% through its life cycle and could last until at least 2027.