This article recently brought up an excellent point on how some rates can be deceiving, and even reduce the likelihood that we will make the right decision. The example involved comparing impressions of fuel efficiency in miles per gallon versus gallons per mile, or gallons per ten thousand miles. While identifying the better of two options in either case is easy regardless of the rate, other types of evaluations can be much more complex if we end up using the wrong units. The main point of the article went something like this. You have an opportunity to increase the fuel efficiency of the two cars in your family. One (a small car) achieves a mileage rating of 32 mpg [miles per gallon], while the other (a large truck) receives a mileage rating of 11 mpg. The two vehicles are used for different purposes, so they cannot be traded for the same vehicle, but they both drive about 10,000 miles per year. The options are increasing the mileage of the small car to 45 mpg or the large car to 20 mpg.
Since you are increasing the miles per gallon the greatest amount in the small car (13 mpg versus 9 mpg), it would make sense to use this opportunity to upgrade the small car to a mileage rating of 45 mpg. Did we make the right decision? It may depend on our objective, but first, let's consider the opportunity from a different angle. [ad name="Adsense Small Horz Banner"] Our vehicles rated by gallons per ten thousand miles come out like this: 313 gptm [gallons per ten thousand miles] for the small car and 909 gptm for the large car. Improving the mileage rating of each vehicle as specified above means that we can reduce their ratings to 222 gptm and 500 gptm respectively. That means that we will have reduced our family gasoline consumption by 91 gallons per year if we upgrade the small car or 409 gallons per year if we upgrade the large car. What a huge difference! Here, there is no doubt that we would chose to improve the large vehicle. Our objective is reducing the amount our family spends on fuel each year.
There are critical policy implications of this kind of logical analysis. One is that advocates for certain policies need to be certain they are using language and units of measure that communicate all that they can. Another is that leaders need to educate the public using the most obvious language and units of measure so that each individual and family can choose the best path.