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Politico quotes Donald Trump :

Just this past week, Trump reveled in a mental list he has been keeping of how many tests the U.S. has conducted, approaching 14 million, in comparison with other countries — Germany at 3 million, Italy at 3 million. That list, like so many others, is designed to ensure American is ranked No. 1. Trump deflected when a reporter asked how America’s testing compared to other countries on a per capita basis, a measure by which the U.S. lags behind several countries.

“You know, when you say ‘per capita,’ there’s many per capitas,” he said. “It’s like, per capita relative to what? But you can look at just about any category, and we’re really at the top, meaning positive on a per capita basis, too.”

It has been a few decades since I was at school. Are there many, or even multiple, per capitas?

Btw, if I ought to be asking this on mathematics, cross validated (statistics), or elsewhere, feel free to migrate it.

Community
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Mawg says reinstate Monica
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    N.B., Webster reports a 2300% one-day increase in lookups for the word https://www.merriam-webster.com/news-trend-watch/trump-there8217s-many-per-capitas-20200521 And that's not the only weird/unintelligible thing he said on that day https://metro.co.uk/2020/05/21/donald-trump-sparks-confusion-saying-tested-positively-towards-negative-coronavirus-12740676/ – Fizz May 24 '20 at 11:39
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    The sentence is unclear. Asking us to parse it will just lead to opinion-based (and probably party-politically influenced) answers – Oddthinking May 24 '20 at 15:26
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    What's opinion-based about it? All authorities agree on the meaning. Unless you mean Trump's opinion. – hdhondt May 25 '20 at 03:50
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    @hdhondt: The relevant question is not "Does the phrase 'per capita' have different meanings in different dictionaries?" as though the claim was a proof-read text from an Economics journal. It is "What did a non-statistician, non-epidemiologist politician with a history of using terminology loosely and vaguely when speaking off-the-cuff mean when he said there were 'many per capitas'? And is that true?" Anything else is attacking a strawman (unless you can show many people believe the literal claim.) And that is opinion-based. – Oddthinking May 25 '20 at 11:15
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    I disagree that this is opinion based. There are not "many" per capitas and I challenge anyone to suggest a plausible explanation of what Trump meant here. – DJClayworth May 25 '20 at 13:18
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    Country A conducted 1000 tests on 500 people from their population of 2000. Country B conducted 1000 tests on 1000 people from their population of 2000. Country C conducts 2 tests per day on patients who previously tested positive. Country D conducts 1 test per week on similar patients. Country E is counting RT-PCR in their figures. Country F is also including antibody tests. There are many different ways of counting, and if some septuagenarian businessman with vague speech styles describes this as "many per capitas", what value are we adding by tackling a strawman? – Oddthinking May 26 '20 at 07:42
  • [Another example](https://twitter.com/jonathanwakeham/status/1264904812342149121/photo/1) - double-counting two samples from the same patient - screenshotted from [here](https://www.thetimes.co.uk/edition/news/coronavirus-in-the-uk-how-many-people-are-really-being-tested-0ln33dp7n). – Oddthinking May 26 '20 at 09:19
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    @DJClayworth I hate to defend the guy but a plausible interpretation if you ignore the overall reliability of the speaker is that it depends on what the denominator is: you'd get different per capita numbers for the whole US vs just the NYC metro, for example. A country with a truly ideal testing system might have a high testing rate per capita in outbreak centers while maintaining low per capita testing overall if it means there are no widespread cases. Of course these don't apply to the US so it's all meaningless anyways, but the specific statement is far from the worst it could be... – Bryan Krause May 26 '20 at 17:05
  • @DJClayworth Also different numerators, such as total tests per person versus tested persons per person (neither of which is a particularly good measure by itself). – Bryan Krause May 26 '20 at 17:07
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    Sorry people, but this is bollocks, There being different measures of how many tests there are does not change the fact that there is only one "per capita". You can measure total number of tests, total number of people tested or whatever, but whichever one is taken "per capita" has the same definition. And Trump is talking about America, so the "per capita" measure is for that. If he wanted to say "New York and Arizona have different per capita measures" he could have said it. – DJClayworth May 26 '20 at 17:36
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    He says "and we’re really at the top, meaning positive on a per capita basis, too". That is simply a lie. – DJClayworth May 26 '20 at 17:38
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    @Brryan "you'd get different per capita numbers for the whole US vs just the NYC metro, for example" - if that is what he meant, he could have (tried to have) said say so. You know, just "use his words". As to the question - no one put words into his mouth, or (mis) interpreted them. As the OP, I am skeptical of them, and would like someone, maybe a professor of statistics, to clarify. Despite the ***opinion*** of @ Oddthinking, this is ***NOT*** an opinion based question. "Per capita" is a widely recognized statistical term with a single definition. – Mawg says reinstate Monica May 27 '20 at 07:10

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Here are a few definitions of "per capita":

Wikipedia: The phrase thus means "by heads" or "for each head", i.e., per individual/person.

Merriam-Webster: per unit of population : by or for each person

Investopedia: Per capita means the average per person

Dictionary.com: by or for each individual person

Legal dictionary: many definitions, all amounting to "to be determined by the number of people"

A quick search will reveal many more, but they all amount to the same thing.

Oddthinking
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hdhondt
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  • This is incorrect. Per capita is in reference to a group of people. In the context of the above quote it means the group of people is the population of some country, but in other contexts it could also refer to the number of sick people or the heirs to some estate or what not. Simply because the term "per capita" does not mean there is only one of them. – PyRulez Jun 04 '20 at 00:05
  • Also, in reading the quote, there is also ambiguity in what is being counted per capita, tests, tests administered, or people tested. So in that sense there it also more than one "per capita" involved. – PyRulez Jun 04 '20 at 00:06