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.
Female participants and the Rock 'n' Roll Series lead the charge.