Accidents with statistics

I read a national news article earlier this year which announced boldly that "You’re more likely to hurt yourself while wearing jandals than high heels, according to ACC data" (Harcourt, 2024). For non-New Zealanders, 'jandals' is the Kiwi term for the concatenation of Japanese sandals. I was intrigued: I wondered what modelling the article writer had used to compare the groups of women - and a few men - who wear high heels against pretty much the entire population over 18 months who might wear jandals.

The answer? No clever comparison. Only raw numbers. The article said, as follows:

"New Zealanders are nearly twice as likely to hurt themselves while wearing jandals than heels, ACC data shows. There were 4200 jandal-related injury claims made to ACC between 2018 and 2022. Injuries involving high heels had 2500 claims, and injuries involving Crocs only had 140 claims in that period" (Harcourt, 2024).

And ACC pretty much said the same thing (2023). These stats are for 4200 jandal accident claims, over five years (ACC, 2023; Harcourt, 2024), which will apply to claims from the entire NZ population regardless of gender who are walking. Say over 18 months of age. Yes, I know that a number of us will not walk due to infirmity or disability, but as a rough rule of thumb, this should be OK.

So I wondered how that compared to 2500 claims for women between 15 and - say - 65 (that is probably a bit generous: most women I know don't wear heels at all). NZ in 2022 had a population of 5,124,100, and 2,581,200 women (Statistics New Zealand, 2022), with 65% of them aged between 15 and 65. Following is the raw population counts of our total population and the likely female heel-wearers (Statistics New Zealand, 2022): 

Year	Total Population	Women aged between 15 and 65
2018	4,900,600	1,618,100
2019	4,979,200	1,638,800
2020	5,090,200	1,671,600
2021	5,111,400	1,668,900
2022	5,124,100	1,664,700

OK. So how many so we need to remove from the general population figures? Those of us who are under 18 month old? Statistics New Zealand to the rescue again (2024):

Year	0 Years	1 Years	2 Years	Age 0 to1 + 50% of Age 2
2018	59,720	60,510	60,960	150,710
2019	59,390	60,080	61,390	150,165
2020	59,730	59,860	61,020	150,100
2021	59,990	60,000	60,310	150,145
2022	61,070	59,980	60,240	151,170

So let's remove the walking population from the total population. That gives us:

Year	Total walking Population	Women aged between 15 and 65
2018	4,749,890	1,618,100
2019	4,829,035	1,638,800
2020	4,940,100	1,671,600
2021	4,961,255	1,668,900
2022	4,972,930	1,664,700

OK, again, I know this is immensely rough, but if we get an average of each group, that is 4,890,642 for the walking population, and 1,652,420 for women (Statistics New Zealand, 2024). And if we look at the percentage of accidents (ACC, 2023; Harcourt, 2024), over five years we get a .086% accident rate for jandals versus a .151% accident rate for heels. It seems obvious that heels are almost twice as dangerous as jandals.

In my view, those who reported on the dangerousness of jandals did not apply common sense. We need to remember to not only report whole numbers, but look at percentages against a population group.  

Sam

References:

ACC. (2023, May 10). Think with your feet to avoid injury. Accident Compensation Corporation. https://www.acc.co.nz/newsroom/stories/think-with-your-feet-to-avoid-injury/#:~:text=Our%20figures%20show%20we%20accepted,injuries%20between%202018%20and%202022

Harcourt, A. (2024, January 9). Jandals are a national icon but they suck. One News. https://www.1news.co.nz/2024/01/09/jandals-are-a-national-icon-but-they-suck/

Statistics New Zealand. (2024). Infoshare: population data. https://infoshare.stats.govt.nz/ViewTable.aspx?pxID=2e075861-c2b5-4db2-93d4-8c8000ad96a1

Statistics New Zealand. (2022, August). National population estimates: At 30 June 2022. https://www.stats.govt.nz/information-releases/national-population-estimates-at-30-june-2022