Who will be the NBA's Most Valuable Player in 2016? According to a collection of NBA general managers, the most likely choice is LeBron James.

This seems like a good guess. James already has been named league MVP four times, and finished in the top five for the award in 10 consecutive seasons. Expecting James to once again contend doesn't exactly seem like going out on a limb—except for one obvious, yet often overlooked factor.

When it comes to NBA player performance, age really matters.

Younger players, of course, can get better with age. In general, though, once players reach their 30th birthdays, they start to curdle like milk. On December 30, James will turn 31.

Rob Simmons and I published a paper that looked at the impact various factors have on NBA performance. Aging was one of those factors, and what we found is that player performance tends to peak around 26. After that, players start to decline: slowly at first, and then precipitously.

LeBron James can still get up, but can he fly as high as he once did? Photo by Bill Streicher-USA TODAY Sports

To better understand how this works, imagine a player is average at the age of 26. What does it mean to be average? Well, an average team will win 0.500 games per 48 minutes. So a perfectly average player, in a sport that plays five at a time, will produce 0.100 wins per 48 minutes.

If a player manages to offer that level of production at 26, there is generally very little change in his performance as he approaches 30. Once the player passes 30, however, the decline becomes steeper and steeper—so much so that by the time that average player is 34, his wins production has entered the negative range:

Consider Michael Jordan. In 1988-89, 25-year-old Jordan posted a career-high in shooting efficiency from the two-point range. He also posted career-highs in rebounds and assists. And if we consider all his box score statistics and translate those into Wins Produced, we see that Jordan's Wins Produced per 48 minutes (or WP48) was 0.390, the highest mark for his career.

In sum, peak Jordan was worth nearly four average players.

As Jordan's career progressed, however, his performance began to slip. By the time he was 29, his two-point shooting efficiency had declined. He was grabbing fewer rebounds and dishing fewer assists. Consequently, his WP48 in 1992-93 was 0.257—still more than twice that of an average player, but not quite Jordan's peak.

After Jordan returned from baseball and passed the 30-year benchmark, the declines started to become more obvious. In 1997-98, Jordan's WP48 was only 0.152. In two seasons with the Washington Wizards, at the age of 38 and 39—let us never speak of Jordan in a throwback Bullets jersey again—Jordan was actually a below-average NBA player.

TFW you're trying to watch Roger Federer, and instead see your reflection in the snow-covered hills. Photo by Robert Deutsch-USA TODAY Sports

Kobe Bryant's career arc is similar. Despite what his fans might think, Bryant's productivity has never come close to what we saw from Jordan. Jordan could routinely shoot better than 50 percent from the field. Bryant has never been able to do this. In fact, Bryant's shooting efficiency for his career is not much different from an average shooting guard; consequently, Bryant's wins production is nowhere near Jordan's.

Nevertheless, Bryant has been a "good" NBA player. In 2003-04, when he was 25, Kobe's WP48 was 0.195 for the Los Angeles Lakers. This remains his career high (and yes, that's about half of Jordan's career high). After that peak, Bryant remained above average, but the last season Bryant reached double figures in wins production was 2008-09, when he was—you guessed it—30. Since then, he's had trouble staying on the court, and when he's there, he isn't what he used to be. Last year, he was one of the least productive Lakers. And this year, as Kobe puts it, he "freaking sucks."

So what about James? His wins production is similar to what we saw from Jordan. James has consistently hit more than 50 percent of his two-point shots. He rebounds and gets assists. In 2008-09, James was 24 years old, and his WP48 was 0.345 for the Cleveland Cavaliers. This remains his career high. Last season, however, James' production slipped: his WP48 was only 0.208. After three games this season his WP48 was 0.205. Yes, it's a small sample, but a sample consistent with last season.

Does that mean James is already in a steep decline? Not necessarily. Aging is only one factor that impacts performance. It's also the only factor that is inevitable_._ Even if James can rebound from a relatively poor 2014-15 this year, his production will erode with time—no matter what he does, getting older will cause him to do it less and less.

Time to give Kobe the "rimgrazer" dunk package in NBA 2K16. —Photo by Kirby Lee-USA TODAY Sports

Still, there's good news for James, and for all those GMs who think he'll be named MVP: a less productive James remains a very productive James, and besides, the award doesn't always go to the most productive NBA player. Published research indicates that the sports media tend to give the MVP award to a leading scorer on one of the best teams. At 31, James definitely could lead the Cavaliers in scoring, and Cleveland definitely could be one of the NBA's best teams.