A top concern for subway riders was once having a purse or wallet snatched. Now, they may be more worried about a sudden attack.

The nature of crime in the subway has become far more unpredictable, even as the number of violent incidents remains low, according to a report released on Friday.

In 2023, for the first time in nearly two decades, the number of felony assaults in the subway system was greater than the number of robberies, according to an analysis of crime statistics by Vital City, an urban policy think tank. The change signals a rise in impulsive violence and a move away from crimes motivated by monetary gain, the report found.

It also reflected a trend in overall crime across the city, which saw a spike in the number of felony assaults in 2024, even as most other major crimes saw a decrease.

Last year in the transit system, there were 561 felony assaults, a major crime category defined as an attack in which a deadly weapon is used or a serious injury results. That number was more than triple what it was in 2009, when 150 felony assaults were reported.

In 2006, robberies and assaults occurred at nearly the same rate, said Elizabeth Glazer, the founder of Vital City and a former criminal justice adviser under Mayor Bill de Blasio. But in recent years, and particularly since the pandemic, violence in the subway has increasingly been driven by animus, frayed nerves and erratic behavior, she said.