It's the start of the last full week of 2015. U.S. stocks are higher in early afternoon trading on Monday, with the Dow Jones Industrial Average (DJINDICES:^DJI) and the S&P 500 (SNPINDEX:^GSPC) up 0.47% and up 0.56%, respectively, at 1:40 p.m. ET.

As the year draws to a close, it's an interesting time to reflect on milestones. In an article published first thing this morning, Bloomberg highlights a notable milestone that was not achieved in 2015 -- but that is only a few months away: With nearly 82 months under its belt, the present bull market rally, which was born from the ashes of March 2009, is on the verge of becoming the second longest in modern times.

The following graph, based on data from Robert Shiller, shows the S&P Composite Index, in Dec. 2015 dollars, beginning in 1970, with each arrow indicating the length of the corresponding stock market rally.

(The S&P Composite Index is the same as the S&P 500 from the latter's inception in 1957. Prior to that, the Composite Index is based on a smaller set of stocks.)

Sp Composite Index
Source: Robert Shiller, Bloomberg.

As is clear from the graph, the current rally, at almost 82 months, is still a ways from overtaking the monstrous 1990s bull market, which lasted nearly a full decade, beginning in Oct. 1990. Nevertheless, it was within a few months' reach of the post-war bull market, which began in June 1949 (not shown on the graph).

What is stunning about this observation is that the present bull market has coincided with a very weak and fragile economic expansion -- nothing like the economic booms of the post-war period or the 1990s.

On the other hand, this bull market has coincided with a huge expansion... in the Fed's balance sheet, the result of multiple rounds of quantitative easing -- not to mention seven years of near-zero interest rates.

As the Fed begins to normalize interest rates, the questions occupying many investors is whether this bull market can continue through 2016 and, if it can't, what will the scale of the damage be? No one knows the answer to that question, but here is what is known:

  • Higher stock prices are unlikely to be the product of an expansion in price-to-earnings multiples, which already look a bit stretched.
  • In terms of momentum, the rally appears to be strained (and perhaps even spent): As of last Friday's close, the S&P 500 was down 2.6% on the year.

All is not lost, however: 2016 may well prove to be the year in which stockpickers come into their own in terms of differentiated results with regard to the index. Speaking of which, Apple is suffering its worst month in almost two years and is in a bear market of its own relative to its 52-week high. To me, that looks like a genuine opportunity for opportunistic, patient capital.

Alex Dumortier, CFA has no position in any stocks mentioned. The Motley Fool owns shares of and recommends Apple. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.