Has USADA drug testing affected the success of underdogs?

Michael Hutchinson looks at betting on underdogs in the USADA era.

Since the USADA drug testing took place, there has been an overwhelming amount of assumptions made on how the testing has affected fighters. One point raised was the effect that the drug testing has had on underdogs, with the narrative gaining momentum after a string of underdog wins in recent events.

The hypothesis is that a fighter who comes into the fight as a favorite might underperform and lose to the underdog if they previously took banned substances. This in no way means that fighters who lost and were the favorites were previously on performance enhancers, but that the rates of underdog victories should increase.

To see if this hypothesis is correct, I gathered the betting data from the 330 fights since the USADA drug testing was implemented. I also collected the betting data from the 330 fights prior to the USADA drug testing.

In order to see if underdogs are winning more than they use to, I put a hypothetical $1 bet on every underdog fighter from pre-USADA and under USADA drug testing. I also calculated how many underdogs defied the odds to win their fights. Here are the results:

Out of the 330 pre-USADA fights, 121 underdogs won their fights (36.7%)

Out of the 330 under USADA fights, 127 underdogs won their fights (38.5%)

Betting $1 on each underdog pre-USADA would earn you a total of $28.97 (8.8% return)

Betting $1 on each underdog under USADA would earn you a total of $40.90 (12.4% return)

The first thing to point out is the very small sample size, which is why the argument that underdogs are winning more under USADA is invalid. A single event can change the amount someone has earned by as much as $27 dollars if betting $1 on every underdog (Fight Night: Bigfoot vs. Mir).

The second thing would be to see the difference in the winning percentages. After 330 fights under USADA, underdogs are winning 1.8% more than they did pre-USADA. This number is underwhelming and shows that the amount of underdog victories hasn’t been significant.

The betting lines do tell an interesting story though. Betting $1 on the 330 fights prior to USADA testing would earn you a 8.8% return on your $330 investment. This number grows by 3.6% when you look at underdog bets post-USADA. Betting $1 on each underdog post-USADA would earn you a 12.4% return on your $330 investment.

On a giant investment, that extra 3.6% could be the difference in thousands of dollars. On the other hand, a difference of 3.6% doesn’t mean that betting on underdogs is a much safer bet than before.

Here are the figures for each individual fight card: