The economics of NASCAR

I've started working on a project that looks at changes over time in competitive balance and earnings differentials in NASCAR, and, so far, the single most interesting piece of data I've dug up is this:

Between 1975 (the earliest year for which data are readily available) and 2009, the number of drivers who appeared in at least on NASCAR race in a year fell from 133 in 1975 to 67 in 2009.

This is, it seems to me, extraordinary.

While I still have to look into this, I think there are two primary potential explanations.

First, NASCAR may have changed the rules governing car design and operations in ways that have significantly increased the costs of owning and maintaining a racing operation. (Safety provisions leap to mind.) This will have the effect of pushing out those car owners and drivers who only occasionally saw a reason to enter a race (e.g., the race was close to home.) Why might NASCAR have wanted to do this? I suspect two reasons.

A. Having a large number of very part-time drivers diluted the quality of the field, even when they managed to qualify. Because these owners/drivers did not compete regularly, they had less competitive cars and less well-honed driving skills. This reduced the quality of the experience for everyone involved. Pushed to choose between an open racing format and higher-quality events, NASCAR (rationally) chose quality.

B. Having less-skilled drivers may have had a secondary effect as well. Car racing is dangerous, and that danger is a part of the spectator appeal. But with inexperienced and less-skilled divers, the risks may be more random, and may be more likely to lead to crashes involving the drivers people do want to see. This could reduce, rather than increase, fan interest.

Second, it could be that many of the part-time participants were older and that the reduction in their numbers was a part of natural attrition. Over time, the drivers and owners attracted to NASCAR may have come to see it as more of a full-time commitment, independent of NASCAR's rules.

I suspect both were involved. But I also suspect my first explanation will prove to be the stronger one.