Risk Assessment for Skydiving versus Grocery Shopping

Do We Have Statistical Data for Trips to the Grocery Store?

A well-connected expert in the American retail grocery industry might know the exact number of annual shopping trips, but that information is not readily available. Nor would it reveal how many person-trips were involved. What do we know about grocery shopping in the USA?

From here on, we concentrate on finding a reasonable estimate, rather than precise statistical data, for the person-trips for groceries.

While we do not need to use the number of American grocery stores, we do note that the Census Bureau considers “convenience stores” to sell some food that would also be found in “supermarkets”. Let’s include all these destinations, both supermarkets and convenience stores, as “grocery stores”.

Make Assumptions for Grocery Shopping

Let’s assume that every person makes one trip to a grocery store every week. Some may walk to neighbourhood convenience stores daily, but on the way to school or work. Others might never shop for groceries, but trust their spouses to buy food at supermarkets. Many younger children go to stores with their parents.

If we count an average of one grocery store visit per person per week, we have 308,750,000 * 52 = 16,055,000,000 person-trips per year.

Make Assumptions for Grocery Shopping versus Other Trips

Let’s assume that every person makes five other round trips per week, whether to school or work. This number is too small for people with active social lives; and too large for some pre-schoolers, those working at home, or confined to long-term care institutions.

Car crashes would certainly account for some deaths during trips.

On these assumptions, only 1/6 of all “local trip” related deaths would involve grocery shopping. That implies 98,841 / 6 = 16,474 deaths.

Using these assumptions, the mortality rate “per 100,000 person-trips” we attribute to buying groceries in the USA in 2010 would be:

• 16,474 / (16,055,000,000 / 100,000) = 0.10 deaths per 100,000.

Concluding the Risk Assessment for Skydiving versus Grocery Shopping

With these assumptions on top of the recent factual statistics for the USA, the comparison is clear.

The rate of death from skydiving is about 0.71 per 100,000 jumps; the attributed mortality rate from trips to the grocery store is only 0.10 deaths per 100,000.

It would be easy to argue that these assumptions grossly overestimate the risk in buying groceries, since many homicides and accidents occur at home or in the workplace. That would simply lower the grocery store mortality rate further, leaving the conclusion unchanged.

If we exclude “convenience stores”, there would be far fewer person-trips to grocery stores per week; again the conclusion is unchanged. It is truly more dangerous to go sky diving than it is to go to the grocery store.

What questions do you have for Decoded Science experts?

References

USPA (United States Parachute Association). Skydiving Safety. Referenced July 28, 2013.

US Census Bureau. United States Census 2010 Interactive Population Map. Referenced July 28, 2013.

US Census Bureau. North American Industry Classification System. Referenced July 28, 2013.

CDC (Center for Disease Control). Deaths: Final Data for 2010. Referenced July 28, 2013.

© Copyright 2013 Mike DeHaan, All rights Reserved. Written For: Decoded Science