Do players drafted as freshman outperform those picked as sophomores?

This year's NCAA freshman class has been getting a great deal of attention, and with good reason.

Expected to be one of the deepest and most important drafts in recent memory, the 2014 class boasts six impact freshman and a top international youngster...and Marcus Smart, the sophomore from Oklahoma State.

Considered to be a top-three pick in the 2013 draft, Smart opted to stay in school for his sophomore year, foregoing money and risking his draft stock. It's a decision he stands by, and one that makes sense when you know his story.

Still, despite having proven more at the collegiate level than any other top-10 prospect, Smart is pegged to go eighth in the 2014 NBA Draft by Draft Express and is number five on ESPN's big board. In both cases, he's the only player in the top-eight who is not a freshman or an international player.

Smart will be 20 years and seven months old when the 2014-15 NBA season begins, the same as freshman Joel Embiid and eight months older than Julius Randle.  Even Aaron Gordon, the youngest of the top prospects, is only 17 months younger than Smart, a relatively small gap if a nine-year career window is considered (nine years is a rookie contract and one max-length extension).

Which is odd, both in economic and basketball terms.

Because first round picks receive four-year contracts and can then become restricted free agents, teams only get four years of hopefully-discounted production from a rookie. Since a sophomore should theoretically be further along, and in some cases more "NBA ready," getting a player further along his development curve should yield more value for a team.

Teams opt for freshman for a number of factors, including youth and the ability to have said development take place under their watch. They may worry that a player has been stunted by repeating a level without increasing the competition level, which may be a real concern in some cases.

As a counter, look at Dwyane Wade and Paul George - yes, these are cherry picked examples, but they are both sophomores who had an important impact within three years, a realistic timeline for a high pick to become a star.

But, as mentioned, those are cherry-picked examples. To get a better idea as to whether older prospects perform better or worse, we used Basketball Reference's Play Index to pull some data. Here's how 20-year old rookies have performed since 2010-11 compared to 19-year old rookies:

Younger rookies do tend to perform slightly better in this limited sample (which is somewhat flawed in that only "ready" rookies will play, and many "high-impact" sophomores actually end up as rookies in the NBA, but alas). In sophomore seasons, we again see only minor separations between the two groups:

There are plenty of reasons to draft one player over another, and so much goes into the draft process that we aren't privy too.

However, the general implication that sophomores are somehow lesser than freshman because of a year (give or take) doesn't hold water. 

In the past four drafts, 15 freshman have gone top-10 to just 13 sophomores and nine upperclassmen; those may have been the right calls based on the players available, but it doesn't mean Smart or another sophomore isn't worthy of being in the discussion atop the draft.