This bull market could be one for the ages if stocks keep going up.
The S&P 500 needs to go up just 6.4 percent from its current level for this bull market to become the greatest of all time, according to Leuthold Group, a firm long known for its market stat crunching on Wall Street.
Leuthold Chief Investment Officer Doug Ramsey said in a note entitled, "Year of the G.O.A.T.?" to clients he thinks this bull market can surpass the one from the 1990s.
The chart below illustrates the cumulative S&P 500 gains from every bull market since World War II:
Source: Leuthold Group
"If the S&P 500 notches a close above 2,717, this bull market will become the Greatest (postwar) cyclical bull Of All Time— eclipsing even the 1990-1998 gain of +302%. It's already been a good year for G.O.A.T.'s, with Tom Brady, Roger Federer, and Floyd Mayweather all cementing their claims. With the S&P 500 less than 7% away, why not?" Ramsey wrote.
The current bull market became the second-best of all time earlier this year. The S&P 500 has risen approximately 14 percent in 2017, led by strong gains in technology and health care shares.
But Ramsey's only strategist on Wall Street who's recently called for more upside to this bull market.
Jonathan Golub, a strategist at Credit Suisse, initiated his year-end 2018 target for the S&P 500 at 2,875, implying a 13 percent upside from the index's current levels .
"Our market views are predicated on a supportive economic backdrop, with benign recessionary risks and a pickup in near-term indicators," Golub said in a note Monday.
The stock market could also see further gains if the Trump administration can move forward with tax reform. Renewed hope for tax reform has recently lifted the S&P 500, along with the Dow Jones industrial average and Nasdaq composite , to record highs.