Jockey Changes in Horse Racing: A Statistical Analysis

When analysing horse racing, one phrase that often stands out on race cards is "jockey change." This notation can influence how bettors perceive the likelihood of a horse winning. A new jockey may pose challenges due to lack of familiarity, while a switch to a more skilled rider could indicate a stable's serious intent to win. This presents two sides of a coin for horse racing enthusiasts.

This article investigates whether horses with jockey changes experience a decrease in betting odds and, critical to our inquiry, if their performance suffers as a result.

Understanding Jockey Changes and Their Frequency

To explore this topic, I studied nearly 37,000 races from the Japan Racing Association (JRA) for 2024 up until the beginning of this year. The horses were categorized based on whether they had the same jockey as their previous race or if there was a change.

Initially, it was clear that a substantial portion of races featured jockey changes. In fact, two-thirds of the races in this assessment involved such changes, marking a prevalent occurrence in the lower-ranking thoroughbreds.

Specifically, about 40% of horses that changed jockeys finished in the 10th position or lower, compared to 30% for those maintaining the same rider. In contrast, only 18% of horses with new jockeys ranked among the top three favorites—indicating that the changes often coincided with less favored entries.

Analyzing Performance Based on Popularity

After recognizing these trends, I aimed to see if biases truly existed in the odds by comparing horses with similar popularity metrics. This evaluation involved two key metrics:

• Win Support Rate: A calculated likelihood of winning based on the reversed win odds excluding the JRA’s takeout, with a benchmark difference of 0.87 points for 2023 statistics.
• Top Three Finishes: The rate at which horses placed in the top three relative to their popularity, using the same metrics to compare over 100 races.

The results were revealing. When popularity levels were matched, horses experiencing jockey changes only displayed a minor reduction in win support rate. The discrepancy was merely 0.41 points in 2024 and 0.32 points in the subsequent period.

Performance Disparities and Factors Contributing to Jockey Changes

Despite the small odds reduction upon switching jockeys, this did not translate strongly into performance degradation. Horses with jockey changes finished in the top three 19% of the time, while retained jockeys finished in that position 25% of the time. This 6% gap illustrates some performance decline, primarily reflecting the challenges lesser-ranking horses face.

Interestingly, the data suggests that many horses experiencing jockey changes were likely longshots, possibly already rated lower due to contributing factors such as less skill or form.

Looking closer at first-time jockey pairings, these horses also performed considerably worse, showcasing a decline of 0.5 to 1.1 finishes in the top three per 100 races. Yet again, this difference fell short of being statistically significant.

The Role of Jockey Ranking in Performance

For context, the analysis also included a ranking of jockeys based on their previous year’s performance. Horses upgraded to jockeys of higher rankings showed a clear initial advantage, finishing in the top three 2.9 times more frequently compared to those downgraded. However, over the years, this benefit diminished, with 2024 numbers only showing a 1.1-time advantage, and slightly negative in 2025-2026.

These findings lead to the conclusion that while jockey changes seem to be common, their actual impact on performance is nuanced and often overstated in the betting market. The focal issue is not merely the change of a jockey but rather the inherent qualities of the horses experiencing these changes.

Conclusion: Reevaluating Jockey Changes in Betting Strategy

The results of the analysis, which show that horses with jockey changes aren't inherently discounted in the betting odds as commonly perceived, should prompt bettors to reconsider their strategies. In essence, the odds reflect a greater inclination towards the horse's popularity than the mere change of jockey.

Moving forward, it is prudent to reassess the significance of a jockey change before deciding how it affects a horse's potential. If the changes are primarily observed among less favored horses, then the subsequent betting adjustments are likely exaggerated. Understanding this might assist bettors in refining their approach to wagering on horse racing.