Why do people keep saying that "rate" is the number of something that happens over a period of time?

I have raised some questions about how "rate" should be used in our forum, and most of the time, people just left the discussion when I still had a lot of questions in my head.

"Rate" is the number of something that happens during a particular period.

This is not only what people told me, but it is also what I found in the dictionary. When I asked if a phrase like the rate of contingent workers per 1000 population was correct, many told me that it was not because of either of these problems:

(1) It must be something that happens

(2) "per 1000 population" is awkward.

Here's my question for each problem:

(1) What about poverty rate, which is the proportion of people living below the poverty line to the toal population of a country? It's not the measurement of those who become poor, it's the measurement of those who are poor. There's nothing happening here. The same question for unemployment rate, and I can name so many more examples like these.

(2) See this table which shows data on the crime rates of different cities in the US. The title is: Yearly Crime Rates per 100,000 people. So why is it okay but "the rate of contingent workers per 1000 population" is incorrect?

I hope you can help me work it out this time. Thanks a lot!

• "flow rate" of water, for example, is measured in units like "gallons per minute". But things like "unemployment rate" are simple ratios, e.g. thefts involving handguns per 100,000 citizens might be the "aggravated robbery" rate.
– TimR
Apr 20 at 20:38
• You said people "leave the discussion" - but this isn't a discussion forum; it is a question-and-answer site. I've answered all 3 of your questions today on rates. I'm the principal data analyst for a large organisation with a team of senior analysts working under me; the only analyst senior to me is a data scientist. I'm starting to think that your questions are straying beyond English grammar and into a technical area that is off-topic. I really hope my answer to this question satisfies you because it isn't good form to ask new question when you don't believe the answer to a previous one. Apr 20 at 21:21
• You'd usually apply rate to phenomena or events, but not to things or people - "unemployment rate" or "car accident rate" works, but "*the rate of unemployed" or "*car rate" doesn't. Apr 20 at 21:51
• It is the raw number per 100,000 that expresses the rate. So you wouldn't say "the rate per 100,000" (though most people wouldn't balk at that). Unemployment rate was 5,000 per 100,000 or 5%.
– TimR
Apr 20 at 21:58
• @Astralbee There seems to be a misunderstanding here. I believe you might not have noticed the time when I created this post. I did it immediately after my three comments on your answer in the other post, BEFORE you replied to those comments. It's not that I didn't believe you because (1) I hadn't even read your responses, and (2) we seem to be in agreement here, aren't we? I posted this question right afterwards simply because I had another point to make and wanted people to discuss it more. Apr 21 at 3:53

I don't think it has to be something that happens. Instead, I would say that rate reflects an amount that varies based on what it is describing. For example:

unemployment rate - amount of unemployment
poverty rate - amount of poverty
crime rate - amount of crime

I don't know why people say that because it's not true. Rates don't need to involve time.

The term "rate" is typically used to describe the number of occurrences of an event or phenomenon within a specific population and/or over a specified period. For example, "the crime rate per 1,000 people". But it isn't time dependant because it can be used in connection with census data (ie a 'snapshot' of time rather than a measured period of time).

I would imagine the reason think a rate must imply something happening over time is because the purpose of calculating a rate is to suggest that rate would apply to any given sample of the same size. For example, to calculate that a vehicle is traveling at 30 miles per hour there is no requirement for the car to travel a mile or for an hour. You could travel for half an hour at 30mph and travel 15 miles, or drive a mile in 2 minutes. The speed (rate) is calculated on available data using a numerator and a denominator and the inference is that, in any hour travelling at that speed, you would cover 30 miles.

Perhaps 'occurs' would be a better word than 'happens' for your quotation. The rate of something doesn't have be timestamped occurrences - it can just be the number of people or things that you would find within a dataset. For example, the word count in a book of a specific word could be described both as the number of times that word "occurs", and the number expressed as a percentage or some other comparison against the total word count could be referred to as the rate at which it occurs.