I don't think "runners tend to be less quantitative about performance gains" is true. There are an enormous number of folks that compete in races and are timed. I would assume most of them care about said time. Also look at the rise of runkeeper, strava, fitbit, garmin and quantified self in general.
Half-marathon fun facts snapshot:
Since 2000, the number of half-marathon finishers in this country has quadrupled (482,000 to 1,960,000) or an impressive increase of 307%.
For the first time in history, 61% of U.S. half-marathon finishers were females (approximately 1,196,000, a record), the highest proportion of any race distance.
Although their percent fell to 39%, there was also a record 764,000 male finishers last year.
Also, in 2013, there were 34 U.S. half-marathons with 10,000 or more finishers (second highest total ever). This data point has doubled since 2009 when there were 17 with 10,000-plus finishers, and in 2000, there was only one.
For the year, there were a total of 42 half-marathons that make up the Top 100 U.S. timed road race list with 15 of them from the Rock 'n' Roll Marathon Series.
The Nike Women's event in Washington, DC last April was the largest inaugural annual half-marathon ever with 14,478 finishers.
Since 2010, 13.1 miles has been the second most popular distance by finishers behind the 5K.
According to Running USA's 2013 National Runner Survey, the half-marathon distance is the favorite race distance by core runners nationwide (preferred 38% by men and 43% by women).
Last year, there were more than 2,100 active U.S. half-marathons (final road race numbers to be released in an upcoming State of the Sport Report).
Per our count, October hosted the most U.S. half-marathons (288), while January had the least (83) in 2013.
October 2013 also produced the most 13.1 mile finishers with more than 312,000 and July the least finishers with just under 53,000.
http://www.runningusa.org/index.cfm?fuseaction=news.details&...
http://www.runningusa.org/statistics
http://www.runningusa.org/index.cfm?fuseaction=news.details&...