One distance is in the decline, while others are booming.
According to Running USA's annual report, almost 2 million people finished half marathons in the U.S. last year.
Half marathons and female runners are the wind in the industry's sails.
The industry continues to show massive growth.
The top 100 largest-timed U.S. road races include 42 half-marathons.
An annual grant of $25,000 goes to a top U.S. training group.
Races with more than 50,000 timed finishers hits a new high.
The Women's Running Magazine Women's Half Marathon Series is the nation's largest women's half-marathon series
Billions of dollars are spent annually on shoes, apparel and race fees.
Nearly 80% surveyed have a college diploma.