Decoding KenPom: A Comprehensive Guide to NCAA Basketball Analytics

The world of NCAA basketball is increasingly driven by data, and one name consistently surfaces in discussions about team performance and tournament predictions: Ken Pomeroy, or KenPom. This article delves into the intricacies of KenPom's system, exploring its key metrics, how it differs from other ranking systems like RPI and NET, and how it can be used to understand and predict the outcomes of college basketball games.

The Rise of Analytics in College Basketball

For many years, the NCAA relied on the Rating Percentage Index (RPI) to seed the NCAA Tournament. However, in the 2019 season, the NCAA transitioned to a new system called the NET (NCAA Evaluation Tool). The NET system has undergone revisions since its inception but remains the NCAA’s official ranking tool. Beyond the NCAA’s official metrics, independent analytics expert Ken Pomeroy offers his highly influential KenPom rankings which has been around longer.

What are KenPom Rankings?

KenPom rankings offer a deep dive into team performance by analyzing offensive and defensive efficiency on a possession-by-possession basis. Pomeroy's site has statistics and metrics for every Division I team in the nation, with the archive section dating back to the 2002 season.

Key KenPom Metrics Explained

When navigating the KenPom site, several key categories stand out:

Adjusted Efficiency Margin (Net Rating): This is KenPom’s primary ranking metric. It represents the difference between a team's adjusted offensive and defensive efficiency. A higher number indicates a stronger team. For example, a team with a Net Rating of 20 would be expected to outscore an average team by approximately 20 points.
Adjusted Offensive Efficiency: This metric estimates the number of points a team would score per 100 possessions against an average team. A higher number indicates a more potent offense.
Adjusted Defensive Efficiency: Conversely, this metric estimates the number of points a team would allow per 100 possessions against an average team. A lower number signifies a stingier defense.
Adjusted Tempo (AdjT): This measures the average number of possessions a team has per game, adjusted to a standard 40-minute contest.
- The formula to estimate possessions per game is: Field goals attempted - offensive rebounds + turnovers + 0.475 * attempted free throws.
Luck Rating: This metric quantifies a team's performance in close games, revealing the deviation from the statistically expected 50% win rate in one-possession games. A positive rating suggests a team has been "lucky" in tight contests, winning more than their fair share.
Strength of Schedule (SOS): KenPom's SOS is based on the average Adjusted Efficiency Margin, Offensive Efficiency, and Defensive Efficiency of a team’s opponents. A higher SOS indicates a tougher slate of games.
Non-Conference Strength of Schedule (NCSOS): This metric rewards teams that actively seek out challenging non-conference matchups rather than easier games.

The "Four Factors" of Basketball Success

Among the most interesting components that KenPom takes into account is what he calls the “Four Factors”: effective field goal percentage, turnover percentage, offensive rebound percentage, and free throws to field goal attempts made. Win these four factors, which together comprise offensive efficiency, and according to KenPom, you have outstanding odds to win the game.

Effective Field Goal Percentage: This statistic adjusts traditional field goal percentage to account for the added value of a three-point basket. It gives a more accurate representation of a team's shooting efficiency.
Turnover Percentage: Limiting turnovers is a key component of any tournament run. This measures the percentage of a team's possessions that end in a turnover. A lower percentage is obviously desirable. Strong shooting teams often have relatively poor offensive efficiencies, due to an alarming tendency to give the ball away.
Offensive Rebound Percentage: The more possessions you generate, the more opportunities you have to score. This measures the percentage of available offensive rebounds that a team secures. A high offensive rebound percentage can mitigate a so-so shooting percentage, as is evidenced by the high offensive ranking of teams like Duke and UNC.
Free Throw Rate: Also known as the ratio of free throw attempts to field goal attempts.

KenPom vs. RPI and NET: Key Differences

While RPI, NET, and KenPom all aim to evaluate team strength, their methodologies differ significantly:

RPI: The RPI was a simple formula based on a team's winning percentage, its opponents' winning percentage, and its opponents' opponents' winning percentage. It heavily emphasized strength of schedule.
NET: The NET is a predictive-learning model that leverages machine learning to simulate game outcomes and constantly compares expected results with actual outcomes, adjusting its model dynamically. The NET heavily integrates game location (home, neutral, away) into its quadrant system, crucially impacting win/loss value. The NET focuses on points per 100 possessions regardless of the pace.
KenPom: KenPom utilizes adjusted efficiency, accounting for a team’s pace of play and number of possessions per game. KenPom primarily focuses on efficiency and predictive metrics; wins and losses are an outcome, not a direct input for its core ranking calculations. KenPom relies on a strict, formulaic (predictive) approach to generate its rankings.

Using KenPom to Predict NCAA Tournament Success

KenPom ratings can provide insight into individual teams and help users break down a March Madness matchup. Teams in the top 25 in both offensive and defensive efficiency often make deep NCAA tournament runs. Teams that are too lopsided (good offense, weak defense or good defense, weak offense), are susceptible to be upset.

KenPom's Predictive Power: An Example

In a given matchup, whichever team had a higher ranking of the factor moved on. In the end, March Madness consists of the undeterred variable of chaos, far stronger than anything KenPom or any site puts out. There’s no “right” way to fill out a bracket, and anyone who tells you otherwise is lying. You’re best advised to sit back and enjoy the ride.

Criticisms and Limitations of KenPom

One of the major criticisms of KenPom ratings is that the system doesn’t account for injuries. KenPom tends to look at the macro, so if a key player is unable to play, the team won’t dip in the KenPom unless the metrics dictate during or after the game.

Accessing and Using KenPom Rankings

Basic metrics are available for free on the KenPom site. More in-depth analysis requires a subscription.

Read also: Crafting Your NCAA Profile

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