Daily Archives: April 19, 2005
Do DUI Roadblocks Work?
For many years now, MADD has focused much of its considerable manpower (over 600 chapters), resources (revenues of $48 million a year) and political influence on the proliferation of DUI roadblocks (or, to use the politically correct phrase, "sobriety checkpoints"). To justify this invasion of our privacy, we have been repeatedly assured that "checkpoints" are extremely effective in reducing alcohol-related traffic fatalities — and these assurances have been accompanied by "statistics". Let's take a closer look at the statistics….
According to MADD's own website, 40 states have checkpoints and 10 do not. Well, it would be interesting to compare the states with the highest percentage of alcohol-related fatalities with the list of states not using checkpoints: If MADD is correct, the states with the highest fatality rates will be the no-roadblock states. Fortunately, another section of MADD's website provides such statistics for each of the states. The 5 states with the highest alcohol-related fatality rates:
According to MADD, all 5 states should be non-checkpoint states. In fact, however, 4 of these states use checkpoints; only Rhode Island does not. Well, what about the 5 states with the lowest fatality percentages? They are:
If MADD is correct about the effectiveness of checkpoints, these should all be checkpoint states. But as with the previous list, only 4 of the states permit the use of sobriety checkpoints; Iowa does not. As with the previous list, the percentage is what one would expect from pure random incidence: 20% of the states (10 of 50) do not have checkpoints — and 20% of the states on each list (1 of 5) do not use checkpoints. There appears to be no correlation between fatality rates and the use of checkpoints.
Let's take a look at another set of statistics: the effect of the proliferation of checkpoints on the national rate of alcohol-related fatalities. If checkpoints are effective, we would expect to find that alcohol-related fatalities will have declined since their widespread acceptance in recent years .
Again, the statistics do not support this. To use MADD's own numbers: Since 1982, the number of fatalities nationwide from alcohol-related crashes has declined every year — until about 1993, when it dropped to 17,908. Perhaps coincidentally, this was the year after the United States Supreme Court ruled that sobriety checkpoints were not unconstitutional. In the 10 years since then, sobriety checkpoints have gained widespead acceptance — but the number of fatalities have levelled off, vacilating between 17,908 and 17,013. Far from supporting MADD's position, one could even argue that this proves sobriety checkpoints have actually halted the steady decline in alcohol-related deaths. This would probably be incorrect — but indicative of how statistics can be used to serve a desired objective.
Incidentally, my favorite example of distorting statistics for self-serving purposes is MADD's own oft-repeated claim:
Since MADD's founding in 1980, alcohol-related fatalities have decreased 44 percent (from 30,429 to 17,013) and MADD has helped save almost 300,000 lives.
300,000? Do the math….