If Coaches Don’t Know Goodhart’s Law, They Should

I recently read a social media post about using statistics in coaching youth volleyball. Pete Wung, a successful junior coach in Ohio for many years, threw out the term “Goodhart’s Law.” I freely admit that I’d never heard of Goodhart’s Law. I put my investigatory hat on and pursued how this concept would impact coaching.

Charles Goodhart

Charles Goodhart, a renowned economist and former Bank of England’s Monetary Policy Committee member, formulated Goodhart’s Law in the 1970s while working at the Bank of England. Goodhart’s Law states that when a measure, such as a performance indicator or metric, is used as a target for individuals or organizations to achieve, it loses its value as an accurate and effective measure. Okay, but this guy was an economist. How might an economic policy have any relevance to coaching club volleyball? Actually, quite a bit!

Zhu Ting, Chinese Volleyball Star

In 2011, the U-18 World Championships were held in Ankara, Turkey. We just completed a match against China, led by future star Zhu Ting. China was quite good, and we had chances to win the match, but for the inordinate amount of attack errors in critical situations. Before our next match against Slovakia, I gave the team a statistical analysis of the China match while lamenting the number of attack errors. I set a performance goal for the upcoming match, focusing on reducing attack errors. Result? We reduced the number of attack errors. How did we accomplish the goal? In my entire coaching career, I’ve never seen so many tips and roll shots in a single match. The players adjusted their game to meet the statistical goals that I put forth. Welcome to Goodhart’s Law.

When a measure (fewer attack errors) becomes a target, it ceases to be a good measure. I wanted the team to make fewer attack errors, so to meet that goal, the attackers became tentative and did everything they could to keep the ball in bounds. Unfortunately, the result was they were also not scoring. The goal of fewer attack errors, while positive with intent, negatively impacted the players’ performance. The goal of fewer errors became the athletes’ focus instead of winning the point or managing the situation. The desired behavior of confident and aggressive attackers took a back seat to error reduction. A learning experience for the head coach!

A recent article about hockey serves as another example of Goodhart’s Law in action. Playing time for this particular team was allocated based on the number of offensive shots on goal while a player was on the ice. The rationale for this metric was the belief that a better level of play by those players on the ice would result in more offensive opportunities, resulting in more shots on goal. Since this metric impacted playing time, and players wanted to play, the players began to focus on the metric (shots on goal) instead of quality shots. They started taking haphazard shots with little chance of scoring. If shots on goal were the metric to get more ice time, the players would take a lot of shots, even if they were poor shots with little chance of scoring. This a classic example of having a positive intent that resulted in unintended negative consequences.

I’ve never been as focused on statistics as some of my coaching colleagues. There is undoubtedly value to various metrics to measure performance, and when used well can impact performance. But I prefer to use statistics to plan practice or work with an athlete individually instead of having statistics used as a Sword of Damocles dangling above the head of the players during practices or matches.

Unintended Consequences

Coaches should know the potential for unintended consequences when using statistics with their teams. For example, the coach desires to increase the velocity of the serve for all the players to above 37 m.p.h. The target isn’t necessarily wrong; however, the unintended consequence might be more service errors or a breakdown in technique as the athlete attempts more velocity on the serve. If the coach focuses more on the proper technique, with the speed of the serve being secondary, the result could be increased speed with fewer errors.

In a recent article, I detailed how I organize most of the time in my practices using constraint activities. Determine your desired behavior and organize an activity that focuses on or reinforces the behavior. For example, if you want to improve serve-receive, create an activity where serve-receive is essential to success. For example, from a live serve, in order to rotate, the receiving team must score five times with a quick middle attack. A prerequisite for a successful quick attack is a good pass. So, the passers are focusing on their passing skills in a game scenario with performance criteria that mandates their undivided focus.  

I will use our match with Slovakia match as an example, where the players attacked with mistake avoidance as their prevailing thought. Here is an activity I might arrange to prioritize being an effective, low-error attacker. First, if a player wants to avoid an attacking error, the tendency is to attack off speed. So, my goal for the attackers was to score while being low-error but attacking with velocity.

The Game – Positive Point
· 6v6, regular volleyball with sideouts, normal rotation, etc.
· Focus- attackers scoring while reducing errors.
· Team A is the starting unit- too many attack errors, or to avoid errors, they hit too many off-speed shots.
· Team B will play a tip coverage defense to defend Team A’s tendency to hit off-speed shots to avoid errors, forcing Team A to attack hard to score. The goal is to prevent Team A from scoring with a tip and force them to score via an aggressive attack.
· Both teams start at 17-17
· Teams can only score by positive plays (aces, stuff blocks, kills). No points are scored on the opponent’s errors.
· However, since we are focusing on making fewer attack errors, there needs to be a consequence for making errors. So, we will modify the scoring. For any error from 17 to 19, the team making the error returns to 17. Errors from 20-24, the team returns to 20.
· You are accomplishing several things; 1) by playing an “up” defense, Team B removes off-speed attack options from Team A. To score, Team A needs to kill the ball via hard attacks while still being penalized for errors; 2) unless they plan on serving a bunch of aces or blocking a lot of balls, Team A has to rely on scoring with high-velocity attacks while avoiding attack errors.

With this game composed of constraints and modified scoring, you establish an environment that promotes aggressive attacks without emphasizing the number of errors made. The players focus on winning the point or game instead of the focus being on fear of making an attack error.

The Takeaway

Avoid having data or a statistical goal become the target for the players. Focusing on a statistical goal will not optimize performance. Statistics do not win or lose games. It simply provides feedback on the winner and the loser. The numbers should be used as roadmaps to assist in planning practice activities and working with players on their skills. Additionally, coaches might use available data as objective feedback to eliminate the guesswork in activities or lineups. However, beating the players over their heads with data will result in unintended consequences that will not align with the desired behavior.