### Driving Safety versus State Alcohol Consumption and State GDP Per Capita

#### by robekulick

When I saw that Allstate publishes a rank of driver safety and also publishes data on average years between accidents for a given person in a number of cities in the United States, my natural inclination was to wonder how alcohol consumption and GDP by state relate to these measures.

Data:

So I threw down my econ text book for an hour and went to work. The results are pretty interesting.

Here is the first regression I did, comparing the allstate rank to per capita alcohol consumption by state, per capita GDP by state, and geographic region:

Linear regression Number of obs = 193 F( 6, 186) = 24.92 Prob > F = 0.0000 R-squared = 0.2351 Root MSE = 49.43 ------------------------------------------------------------------------------ | Robust rank | Coef. Std. Err. t P>|t| [95% Conf. Interval] -------------+---------------------------------------------------------------- alcohol | 3.522978 12.44198 0.28 0.777 -21.02257 28.06853 gdp | .0014079 .0005037 2.80 0.006 .0004142 .0024015 east | 5.043339 13.26603 0.38 0.704 -21.12789 31.21457 midwest | -79.25639 13.47801 -5.88 0.000 -105.8458 -52.66697 south | -48.17839 12.53827 -3.84 0.000 -72.9139 -23.44289 west | -54.58543 11.63552 -4.69 0.000 -77.53999 -31.63086 _cons | 78.76122 34.10407 2.31 0.022 11.48071 146.0417 ------------------------------------------------------------------------------

For the second I replaced the rank variable with the accident years variable:

Linear regression Number of obs = 193 F( 6, 186) = 16.71 Prob > F = 0.0000 R-squared = 0.2931 Root MSE = 1.4048 ------------------------------------------------------------------------------ | Robust ayears | Coef. Std. Err. t P>|t| [95% Conf. Interval] -------------+---------------------------------------------------------------- alcohol | .013753 .3724981 0.04 0.971 -.7211113 .7486173 gdp | -.0000536 .0000125 -4.29 0.000 -.0000782 -.0000289 midwest | 2.56402 .3887997 6.59 0.000 1.796996 3.331044 south | 1.662039 .3538296 4.70 0.000 .9640036 2.360074 west | 1.959656 .3447658 5.68 0.000 1.279502 2.63981 other | 2.187849 .3539057 6.18 0.000 1.489664 2.886034 _cons | 9.690933 .9040911 10.72 0.000 7.907342 11.47452

For the third I used the natural log of the accident years, alcohol, and gdp variables:

Linear regression Number of obs = 193 F( 6, 186) = 23.70 Prob > F = 0.0000 R-squared = 0.3532 Root MSE = .15124 ------------------------------------------------------------------------------ | Robust lnayears | Coef. Std. Err. t P>|t| [95% Conf. Interval] -------------+---------------------------------------------------------------- lnalcohol | -.0844827 .0940677 -0.90 0.370 -.2700594 .101094 lngdp | -.4183175 .0642201 -6.51 0.000 -.545011 -.2916241 midwest | .2745044 .0504288 5.44 0.000 .1750186 .3739903 south | .1704175 .047285 3.60 0.000 .0771336 .2637014 west | .231661 .0467611 4.95 0.000 .1394107 .3239113 other | .3002159 .0535485 5.61 0.000 .1945755 .4058564 _cons | 6.533847 .6644993 9.83 0.000 5.222923 7.844771 ------------------------------------------------------------------------------

So what does this all mean? Well interestingly enough the effect of alcohol is not statistically significant in any of the regressions. Furthermore, the relationship between driving safety and GDP is statistically significant, but the two variables are *inversely related*. So drivers are less safe in wealthier states. Finally, and this won’t surprise anyone, drivers in the Midwest, South, West, and Alaska and Hawaii (my other category) are safer than drivers on the East Coast on average.

Now at this point I need to say something very, very, very important. THIS ABSOLUTELY DOES NOT INDICATE DRINKING AND DRIVING IS SAFE. We know for a fact it is not. But what this does mean is that some characteristic of states with higher levels of alcohol consumption is preventing this increase in translating into more traffic accidents. One possibility is that though people in some states drink more, they are no more likely to drive while drinking. Another possibility is that states with high alcohol consumption have stricter laws that reduce traffic accidents.

I’m not sure what to make of the fact that per capita GDP is inversely related to driving safety. I have to admit my thought was that after controlling for regional variation, the relationship would be positive.

And of course, anyone who has spent a significant amount of time on the east coast knows drivers here are crazy. One interesting question though is whether the Allstate measures effectively control for all of the effects of increased traffic on accidents. My initial thought was that by measuring things in terms of average time between accidents, the effects of higher traffic should be implicitly controlled for. But that probably calls for more research.