STUMP » Articles » U.S. Motor Vehicle Accident Deaths: Seasonal Patterns and June 2023 Update » 6 June 2023, 05:42

Hello, new readers! If you haven’t seen this, check out an orientation to this substack. That will get you familiar with the common topics here — including DEATH.

There was an update today to CDC WONDER, the main database for death statistics that I use, so I thought I’d take advantage by making a few graphs.

Seasonality of Motor Vehicle Accident Deaths

Most people are used to the seasonality of deaths, as old people tend to die in the winter from pneumonia and heart disease. Other causes of death don’t have a seasonality to them, such as cancer.

There is a seasonality to motor vehicle accident deaths.

As when I first wrote about motor vehicle accident deaths, there are peak times for them, and they tend to be around holidays. Summer holidays. And yes, drunk driving is heavily involved.

The lowest point every year is usually January or February. As I’ve normalized for month length (and yes, I took into account leap years, thanks for asking — you can check by downloading my spreadsheet at the bottom of the substack post), it’s not because February is the shortest month.

It’s because it’s difficult to die in a motor vehicle accident if you’re not driving anywhere. If you’re snowed in… you’re not driving. If you’re not going on vacation, you’re not driving.

Within one year, there is a lot of variability. To measure this, I take the difference between the maximum and the minimum and compare it as a percentage of the average over the year. Over the period we’re looking at, this variability ranges from 20% – 30%.

Highs and Lows

I picked out four points on that graph to highlight local lows and highs.

The low for the period occurred in February 2010, when there was only an average of 77.9 motor vehicle accident deaths per day.

Before that, the local high had been in July 2007, at a high of 141.6 deaths/day. The most recent high occurred in October 2022, at 144.6 deaths/day. Interesting it took 15 years to get back to that level… and that’s not a good thing.

The fall in deaths from 2007 to 2010 was in line with a long-standing pattern that actuaries have seen: in general, motor vehicle accident deaths have increased with increasing economic activity and decreased during recessions.

You can see notable decreases in motor vehicle accident death rates during recessions — the one in the early 1970s was the oil embargo, so that was particularly hard-hitting in terms of the number of miles people were driving. Also, people weren’t quite driving as fast.

But you can see that in many periods of economic growth, motor vehicle accident death rates climbed, and then dropped during recessions… except for short-lived ones.

To be sure, during the 1990s and 2000s, rates went sort of sideways. Similarly, the 2010s saw rates stay pretty low. I’m not showing you what happened with rates per millions of miles driven — they really did improve. Vehicles were getting safer, with airbags as well as other safety features.

But you see that anomaly during the pandemic – in 2020, motor vehicle accidents did jump up.

Focusing on the pandemic period

Let’s just focus on 2018-2022 (I have to stop at November 2022, as the current data update gets me only the first week of December motor vehicle accident deaths. External deaths — homicides, suicides, and accidental deaths — are not made available in the statistics for 6 months, due to investigative reasons.)

I picked out 4 different points this time — two local high points for 2018 and 2019, both of which were in September. In general, in most years, the high point for motor vehicle accident deaths is sometime in the 3-month period of August – October. September is a very common month, though, due to Labor Day.

Then there is the local low point of April 2020, when many people were locked down, and not driving anywhere.

Then I picked out January 2022 — it was a low point for 2022, and January tends to be a low point for most years.

But I picked it out specifically so you could compare it against the rates in 2018 and 2019. That low in 2022 is only a few percentage points below the high from the pre-pandemic rates.

If you were wondering why your auto insurance rates had gotten so high… well, other things are involved as well. Inflation of various sorts, non-fatal accidents, and theft — these add to insurance costs, too.

But death is a pretty serious business as well.

Spreadsheet

Spreadsheet can be downloaded at the substack post