The overall fatality rate for Thoroughbred races held in North America in 2017 inched up slightly to 1.61 per 1,000 starts, according to data released on Monday by The Jockey Club.

The increase from the 1.54 rate in 2016 reversed several years of declines, but the 4.5 percent rise was not considered statistically significant by Dr. Tim Parkin, the epidemiologist who studies the data. Since the data began being collected in 2009 in a project called the Equine Injury Database, the overall fatality rate has dropped from 2.00 per 1,000 starts.

“Although fatality rates increased this year from last year, the increase in rates is not statistically significant,” Parkin said, in a release. “However, the overall decline in the rate of fatalities since the creation of the EID is statistically significant and reflects a continuously improving safety record for North American racing.”

As has been the case in previous years, the fatality rate on dirt was higher than the rate for both turf racing and racing on a synthetic surface. The dirt rate in 2017 was 1.74 fatalities per 1,000 starts, compared to 1.36 on turf and 1.10 on artificial surfaces, according to The Jockey Club.

Also in line with previous years, the fatality rate for 2-year-old horses was lower than the rate for older horses. The 2-year-old rate in 2017 was 1.32, compared to 1.62 for 3-year-olds and 1.53 for older horses.

The fatality rate for races run at less than six furlongs in 217 was 1.66, while races run between six furlongs and a mile had a fatality rate of 1.62. Longer races had a rate of 1.53.

The overall rate declined slightly from 2009-2014, but the rate then dropped significantly in 2015 and dipped again in 2016. Racing officials have credited efforts by racing commissions to exercise more vigilance in pre-race exams and a tightening of medication rules for the declines, and it is also widely believed that horsemen are exercising more caution with their horses, due in large part to growing awareness of the impact of fatal injuries on the sport’s image.

Data in the EID is collected from racetracks representing approximately 97 percent of the starts in North America, the Jockey Club said.