The S&P 500 Index (SPX​) should reach a record 2,800 by the end of 2018, more than 7.5% above the open of trading on Monday, based on the average forecasts from nine market strategists polled by Bloomberg. Some strategists forecast stocks could rise as much as 27 percent. Those gains would create the longest bull market on record. Key reasons for their continued bullishness, per Bloomberg: even without tax reform, corporate earnings in the U.S. are rising at a double-digit pace, and the global economy is showing its most consistent growth in more than a decade.

Most of these strategists did not put assumptions about tax reform into their forecasts, Bloomberg notes. The most bullish tax reform scenario is offered by strategist Keith Parker of Swiss banking giant UBS Group AG. Parker has a base case of 2,900 for the S&P 500 in 2018, up 11.5% from today's opening, but he projects that the index could reach 3,300, up 26.8%, if corporate tax cuts take effect in 2018, Bloomberg says.

Market Leaders

In the capitalization-weighted S&P 500, the five so-called FAAMG​ technology stocks currently account for about 13.8% of the index's value, according to SlickCharts.com, and thus are key drivers of the S&P's gains. These stocks are, in order of weight from highest to lowest, and with their year-to-date gains through November 24: Apple Inc. (AAPL), +53%; Microsoft Corp. (MSFT), +37%; Google parent Alphabet Inc. (GOOGL and GOOG), +35%; Amazon.com Inc. (AMZN), +58%; and Facebook Inc. (FB) +59%. The S&P 500 rose 16.2% over the same year-to-date period.

Broad Rally

While the five soaring FAAMG stocks have had an outsized influence on the S&P 500, there nonetheless are indicators that the 2017 rally has been broad-based. Chris Verrone, head of technical analysis at Strategas Research Partners, calculated early last week that more than 70% of the S&P 500 stocks have posted gains, and that the spread between the cap-weighted S&P 500 and an equal-weighted version is not excessive. (For more, see also: Why the 'Santa Claus" Stock Rally Is at Risk.)

Meanwhile, the stock market's advance has been a global phenomenon. Among 35 indexes that track the stock markets with the biggest capitalizations around the world, at least half have set new all-time records in 2017, per analysis by The Wall Street Journal. This is the best showing in this respect since 2007, the Journal adds. While leading indexes in Japan, Hong Kong and Taiwan have not reached new all-time highs in 2017, they nonetheless have exceeded values last seen years ago, respectively in 1996, 2007 and 1990, per the Journal. (For more, see also: Global 4% GDP Growth Can Fuel Stocks in 2018: Goldman.)

Bullish Bias

Investors should note that market strategists have a long history of bullish bias. Since 1999, U.S. market strategists tracked by Bloomberg never have predicted a stock market decline for the upcoming year, instead calling for an average annual gain of 9% during this period. A particularly notorious case was 2008, when the S&P 500 plummeted 39%. The consensus forecast had called for an 11% gain.

On the other hand, even the most bullish strategists polled in January were not predicting a 16% advance for the S&P 500 this year, Bloomberg adds. In fact, the current bull market has outrun strategists' expectations by about 3.8 percentage points per year since it started in March 2009, Bloomberg says.

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