For example, I recently read some data from the United States Postal Service Greenhouse Gas Emissions Survey that had some impressive data. By replacing just two trips to the mall each year by shopping by catalogs or direct mail, Americans could:
- Save 30 miles per household – or 3,332,718,510 miles per year.
- Save 158,700,881 gallons of gasoline or about $634,803,524.
- Avoid 28 tons of CO2 emissions per household – or 3,094,667,179 tons per year.
Sounds great. Sign me up! Then I started thinking about it some more.
Americans may save that many miles, but does that mean that the miles aren’t traveled? No, those products still need to get delivered, and that takes gas.
If the packages are being delivered by the USPS — even if the mail carrier is coming to your house anyway — the delivery is not carbon-footprint-neutral. Every additional package being delivered adds extra weight that requires additional fuel. I wonder if that additional weight is factored into the USPS calculations?
If another carrier is used to deliver the package, how far out of the way are those carriers traveling to deliver those packages? The miles saved by the consumer not going to the mall are offset by the number of miles the delivery service must go to deliver their purchase to their house.
The USPS estimate assumed 7.5 miles, on average, to a local mall (15 miles round trip). That’s not an insignificant distance — a full gallon of gas for the average SUV. Delivery services will likely save miles overall. But few people make a trip to the mall to purchase a single item. Usually that trip is combined with other errands. So can you really assign the full 15 miles round-trip to that purchase? Contrast this with a package delivery to your house. That’s usually a dedicated stop.
Then there is the weight of the delivery trucks. There is a lot of weight (and fuel) associated with these vehicles. While drivers may be extremely efficient delivery routes, they are also making regular stops and starts, often in city traffic, which burns up far more gas than the average passenger vehicle going to the mall. Plus, did the USPS factor in the fact that these trucks are kept running at every drop-off?
I could go on, but you get the point. I tried to find the original source for the USPS estimates (here’s one of them), but I was unsuccessful. Lots of PowerPoint and other presentations have cited these numbers, but in some ways the source is irrelevant because that’s not the point. The point is that we must look at such data with a critical eye.
What is being said? What is not being said? What is being excluded? Are these data giving the full picture or just the biased slice that the author wants us to see?