001.008 Disqualifications

A small number (3%) of age group swims result in a disqualification, ie., an observed violation of USA-S rules.  We only count disqualifications where the swimmer attempted to swim the event, excluding no shows and declared false starts.  While most disqualified swims include a time in our data, our analysis does not consider the times of disqualified swims.

This post will examine the statistics of disqualifications.  We’ll learn that disqualifications decline with athlete age, are more likely for men than women, and are more likely for short-course events than long-course events.

Age.

The likelihood of a swim being disqualified declines rapidly with age.  Indeed, age is the most significant predictor of a disqualification.

Gender.

All other things being equal, men are 1.26 times as likely to be disqualified as women.

While the relative likelihood of disqualification narrows with age, men are more likely to be disqualified than women at all ages.

From ages 11 to 13, male swims are at least 1.4 times more likely to be disqualified than female swims.

Course.

The likelihood of a disqualification is significantly greater for SCY events than LCM events.


The disparity in SCY and LCM DQ likelihoods is partially due to an age effect.  Younger athletes (who are more likely to be DQed) swim more SCY events than LCM events, while older athletes (who are less likely to be DQed) swim more LCM events than SCY events.

While age is a contributing factor, the following plot establishes that age is not the only factor in the DQ disparity.  It shows that even after controlling for age, 12/Under SCY swims are almost twice as likely to be disqualified as 12/Under LCM swims.

From ages 9 to 12, SCY swims are more than 1.6 times as likely to be disqualified as LCM swims.

Two plausible explanations for this course disparity lie with USA-S officiating.  


Officiating Density Hypothesis.  SCY and LCM meets typically have similar numbers of stroke and turn officials.  Since LCM events have more than twice the surface area of SCY events, LCM swims must receive less attention from the stroke officials on average than SCY swims.  This hypothesis predicts that the likelihood of stroke DQs decreases with lane count, all other things being equal. In other words, we should see the most stroke DQs in a 6 lane SCY event and the fewest in a 10 lane LCM event, all other things being equal.


Turn Count Hypothesis.  Many disqualifications occur in turns, whose execution is closely judged by officials positioned at both ends of the pool.  SCY swims have more than twice as many turns as LCM swims, and hence have more than twice as many opportunities for a turn disqualification.  For example, a 50 Back swim has one turn in a SCY event but none in a LCM event. A 100 Back swim has three turns in a SCY event but only one in a LCM event.  A 200 Back swim has seven turns in a SCY event but only three in a LCM event. Note that the ratio of SCY turns to LCM turns is greatest in the shorter events favored by younger athletes, compounding the problem.  This hypothesis predicts that the likelihood of turn DQs increases with increasing turns, and that the ratio of SCY DQs to LCM DQs is greatest for shorter events, where the ratio of SCY turns to LCM turns is greatest.


As further evidence for the Turn Count Hypothesis, please consider the following chart, which shows that the disparity between SCY and LCM backstroke disqualifications.  In my experience, most backstroke disqualifications occur in the turns (delay initiating the pull, or delay initiating the turn), so it would make sense that backstroke events with more turns would result in more disqualifications.

Stroke.

As expected, freestyle is the event type least likely to result in a disqualification. The event type most likely to result in a disqualification is IM, followed by breaststroke.


As previously seen, every stroke is more likely to be disqualified in SCY than LCM, with IM and backstroke having the greatest course disparity and freestyle the least.

The likelihood of a freestyle DQ is the lowest at all ages, and declines the least. Of the remaining event types, the likelihood of a butterfly DQ declines the most with age (29.3x), while the likelihood of a backstroke DQ declines the least with age (7.2x).

The age-related decline in DQ likelihood (from age 6 to age 18) is shown in the following plot.

My anecdotal experience is that butterfly DQs for younger swimmers are predominantly due to difficulty of recovering both arms simultaneously over the water, which becomes easier with practice and age-related strength gains.  Backstroke DQs are mostly in the turns, whose timing is difficult to master and changes from season to season because the backstroke flags are in different positions for SCY and LCM events.

Events.

Put all that together, and the event most likely to result in a DQ is the 100 IM, which is only recognized for 12/Unders in the short course.  The 100 IM combines the stroke most likely to be DQed (IM) with the course most likely to DQed (short) and the age group most likely to be DQed (younger).

Disqualification Report Codes.

Disqualifications are reported on a “Disqualification Report”, which identifies the USA-S rule infraction via a set of two character DQ report codes.  For example, the code “1A” would indicate that the swimmer used an alternating kick in a butterfly event, while code “3J” would indicate a one-hand touch in a breaststroke event.


Initially I hoped to provide the distribution of DQ report codes, to better understand the causes of disqualification by stroke and age.  Unfortunately, the DQ report codes are not used consistently across our data set. Their meaning changes over time and varies across LSCs.  For example, the code “3B” is variously used to indicate four different breaststroke rule infractions: butterfly kick, non-simultaneous kick, incomplete stroke cycle, and head did not break surface of the water.  The code “2E” is variously used to indicate four different backstroke rule violations: delay initiating the pull during turn, multiple arm pulls during turn, not on back at finish, and toes over lip of gutter at start.  I estimate that there are at least four incompatible DQ report code interpretations in our data, and it would be a significant undertaking to map them to the universal coding system required for meaningful analysis.

Conclusion.

We’ve seen that the likelihood of a disqualification declines greatly with age, as athletes become stronger and more skilled.  Regardless of age, freestyle is the event least likely to result in disqualification while individual medley is the event most likely to result in disqualification.  We’ve also seen that disqualifications are substantially more likely in SCY events than LCM events.