2013 Ratings Update: Sonoma


[NOTE: Toward the end of each week, I will review the previous race's U.S. Nielsen rating and how it fits-in historically. I would love to read your opinions on how and why ratings at each track have changed over time. You may send me your commentary on Twitter at or via email at .]

Well, “NASCAR on TNT” finally broke the 3.0 threshold for the first time this season with their telecast of NASCAR’s Cup Series race at Sonoma. The network’s first two events of 2013 — Pocono and Michigan — earned identical 2.8 ratings. So before I write about TNT’s path to a small week-over-week increase, I present a table that lists the historical record of Sonoma on television:

Just like last week’s entry on Michigan, I calculate a rating called “if_tnt” that gauges what the television audience would have been if the race were on TNT in that year. I generate this hypothetical number from my model so that I can get a better sense of the real trend — unadulterated by the television element that can influence viewership heavily — that an event’s interest has drawn since 1996. Here is a line graph that plots each “TNT rating” for the Sonoma race:
Like most races I’ve reviewed this year, Sonoma’s television interest peaked in 2005. The track has exhibited a rather steep decline in household audience, however, since 2006. Although 2011 and 2012 demonstrated a slight comeback for the road course, this year’s edition garnered a 3.0 — down from last season’s 3.3.

All of that is pretty intuitive; it follows along the traditional rise-and-decline of NASCAR’s popularity over the past 18 years. What is not immediately understandable, however, is why Sonoma consistently outdraws several ovals on the schedule. After all, road courses are the least-watched track configuration:

The key to Sonoma’s success is that the facility is located on the West Coast. In fact, the further west a track is situated, the better rating it will earn — all other race characteristics held constant. Events held out west, i.e. Fontana, Las Vegas, Phoenix, and Sonoma; accommodate a later start time in the Eastern time zone. When a race begins at 3pm/ET instead of noon, for example, more people are available to watch. Sunday traditions like church and brunch are completed by the late afternoon, so a greater number of fans have an opportunity to watch a NASCAR race. To bolster further the number of people watching, races out west commence at a convenient time for those in the area. Rather than having to catch a Martinsville race that starts at 9am/PT; someone in, say, California doesn’t have to tune-in for a race at Sonoma until noon. Thus, that late-afternoon green flag expands the pool of fans who can catch a Sunday race. Here’s a nice bar graph that helps visualize the point:
Keep in mind that this chart already controls for the economy, the Chase, N.F.L., event prestige, television network, time of race, and track configuration. After we take those features into account, tracks located in the Pacific time zone draw a household audience that’s approximately 9.7% bigger than similar facilities on the east coast. That means that the Sonoma race would have received an underwhelming 2.7 if it were located out east (or, similarly, if the green flag were dropped around noon/ET). Though attendance figures might contend the conclusion to this type of discussion, holding west coast races (or perhaps starting east coast events in the late afternoon) is a great way for NASCAR to expand its coverage into more television households.

“NASCAR on TNT” has made it half-way through its six race “summer series” in 2013. How accurate has my econometric model predicted this season’s television ratings? Perfectly accurate in a statistical sense — I’ve not missed the mark on any race yet:
My model calls for a 2.8 household rating for Saturday night’s Kentucky race. I think it will be tough for TNT to meet that — the network seems to have struggled with keeping afloat from last year’s totals. In 2012, this particular event only drew a 2.5 (it earned a 3.0 in 2011, but that race was scheduled one week after the mid-season race at Daytona).

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