Gas Tax Math

Thank you to Rep. John Mann for this explanation:

The gas tax increase that the NH Legislature passed this past spring presents a neat “teaching moment” both mathematically and politically. The increase has been described as “only 4 cents” – but also as a 23% tax increase. (Yikes?)  And there is yet another way to describe it: as a mere 1.2% increase in the cost of gasoline (assuming gas at $3.50 a gallon).

Writing as a former high school math teacher I see this issue as a  great example to illustrate to students the value of “numeracy”.  Numeracy is to numbers as literacy is to language. Facility with numbers helps one to examine a situation from all sides.  Numeracy means being able to examine and evaluate someone’s mathematical claim, just as literacy means being able to not only read a word or a sentence but to comprehend a letter or a speech well enough to evaluate what is presented.  The goal of both literacy and numeracy is to help people figure out “what to believe”.

From the Department of Transportation’s point of view, this is indeed a 23% increase – in tax revenue.  This is good – it will enable DOT to begin to repair our neglected roads and bridges.

The 23% view is useful also to opponents of the tax increase, because it makes the increase look as bad as possible.   For someone looking for a juicy headline or sound bite, the 23% number is difficult to pass up.  Not all reporters or citizens will think twice, so a news clip about a 23% tax increase might sway some voters and the prospect can scare politicians.

But for most people it is a very small tax increase, and necessary to keep the roads in reasonable shape.   The consumer does not see a 23% jump in anything.

In fact, there are a couple of interesting things about a 1% increase in fuel costs.  One is that a driver can avoid paying the increase by driving just a little slower, since at Interstate speeds, faster speed means reduced miles per gallon.  And it turns out that (for instance) for the trip from Salem, NH to Colebrook, NH, which is 175 miles and 3:08 of time per Google Maps, we’d arrive only 3.5 minutes later if we averaged 1 mph slower.  The second thought is related to a news report that the average vehicle damage just this last winter, due to road issues, was $350. To pay out that much from the tax increase a person would have to buy almost $30,000 worth of gasoline.  How many years would that take?  Maybe it’s better to pay for road maintenance rather than suffer vehicle damage.

This isn’t math used to “get an answer” or to “solve a problem”.   It’s math used to explore something, to understand it.  Therefore, this looks to me like an excellent and relevant case study, where democracy meets arithmetic – which every math teacher can bring to school next fall, to help their charges become good decision-makers (and voters).


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