How stable is a "generation"?

Have we lit upon a definition of “a generation” that is stable over time?

It seems to me that the average age that a parent (of either sex) has his or her children constitutes a generation, no? Is this an acceptable measure of what makes for the length of a generation?

If so, we should be able to track things like the length of a generation in the sixteenth century and the twenty-first pretty accurately. Or the length of a generation in the U.S. and in Tahiti.

Or is a generation’s definition more complicated than simply figuring out the average age at which parents have their children?

When it comes to family genarations I think that part of the definition of a generations needs to include your cousins of similar age and experiances. Same for a broader definition of generations that includes society as a whole, shared experiances. I’m 62 and people of my genearation can tell you all about that 70’s experiance without referances the TV show becasue we lived it together.

If you didn’t wear bell bottoms at some point, listen to the first Beatles songs on an AM radio or didn’t actually used an 8 track (or know what it even is), then you are not a part of my genearation.

Not sure there can even be a factual answer that covers everyone becasue it can mean a couple of differnt things whether you are talking family or social geneartions. But in the most simple case I think that you have it, parents and their children define the basis of a genaration, so that definition is pretty stable.

Many people, including myself, consider a “generation” to be about 20 years or so. The older generation gives birth to the next generation and raises it to adulthood. Rinse and repeat.

20 years? Maybe in the good olde days… I have variously seen a generation referred to - when counting elapsed time in “generations” as either 25 or 33 years, to neatly fit into a century. 25 seemed like a good number for more than 50 or 60 years ago, but the last generation or 3, it seems people tend to wait until late 20’s or early 30’s to have children.

In terms of boomers, genX, Y, Millennials, etc. nuestro Amigo has it right I think - a generation is defined by shared experiences and environment, the tenor of the era in you grew up.

Years ago I saw a teaching video by Morris Massey, “What You Are Is What You Were When” that discussed that a generation grows up surrounded by a certain factors which fix their outlook on life. Who were your heroes? What was society fixated on? (He’s fun to listen to if you can find it). A good example (from the 80’s) he said he was consulting for a large firm. The supervisors complained about the work ethic of the younger workers. Someone screws up, they would say the standard punishment “take a day off without pay to think about your job.” For people who grew up in the depression, a job was important. The young 'uns who grew up in the 70’s would reply “A day off? I’ll take two!” Confused the heck out of the bosses. Massey said the younger people grew up with plenty, jobs were everywhere, they didn’t worry about it, leisure time was more important. (His solution - instead of sending the screwup home, make him stay late and fix his mess. They hated that and avoided screwing up in future.)

Depends on which sort of generation you are talking about - you have generations within a family which can overlap , where one generation is the parents, then their children, then their grandchildren. These generations can overlap - it’s not terribly uncommon for someone to have a child younger than a grandchild.

Then there are the generations that might be best called a cohort- they are approximately 20 years, some a bit more and some a little less ( The “Greatest Generation” is 1901-1927 while “Generation X” is 1965-1980) and based on common experiences. These generations are completely separate from the familial ones - one of my uncles is a generation ahead of me in the family , but he was born at the beginning of the Baby Boom and I was born near the end while my 18 years younger cousin is a Millennial.

I guess what I’m asking is more precise than just “what people think a generation is.” It seems to me that we (the whole of a society) can define, on average, exactly what makes a generation. If you took all the parents in the US and wrote down their ages when they had each child, added the totals, and divided that number by the number of parents you’ve included, you’d get a very precise figure, which would (I suppose) differ from a similar study done a hundred, or three hundred, years earlier, and also differ from a similar study done in China or in Peru.

Has anyone done this, or anything like this?

I suppose someone might have figured out the average age at which currently alive parents had children - but I’m not sure what use it would be. If you aren’t talking about about either shared experiences or position within a given family, I’m not sure what the purpose would be of saying a generation is 16 years or 30 years or whatever it turns out to be. You will have a lot more overlap - let’s say a generation is 30 years. Am I in the same generation as my mother, who was 22 when I was born or my daughter , who was born when I was 26 ? And there will be changes- maybe when I was born a generation would have only been 18 years. Was I in a different generation from my parents when I was born and it later changed to the same generation?

Well, considered generationally over a period of decades, the number might (or might not) differ considerably, and that would tell us things about society.

For example, say you had some families you could trace back with some accuracy for 10 generations in the US and in China. (I’m sure there are some in each country.) If the 10th generation in one country took you back, on average, to 1720 and in the other one took you back to 1750, wouldn’t that say things, perhaps significant things, about each country? And if both countries were much closer, or identical, wouldn’t THAT tell you something significant about the human race?

But that’s jumping the gun. I’m just trying to figure out if anyone has studied this stuff.

That’s not really possible since “generation” means different things in different contexts. There are critical definitional differences between a genealogical generation and a cultural one.

If you want a firm definition, start by firmly establishing a context.

Maybe I’m misunderstanding you - but how can you talk about tracing a family back 10 generations if a generation is going to consist of some number of years calculated over the entire population that exists at a certain time. Or are you proposing a third, unrelated meaning for “generation”.

People generally study things for a reason - you can certainly find out what the average age was for women giving birth in the US in a particular year was. But I don’t think that’s what you’re talking about. I think what you are talking about is a number that will have one value in 2023 , and a different value in 2024 ( as parents die and no longer contribute to the calculation and more people become parents and are added to the calculation. ) Suppose a lot of parents died between the date of the survey in 2023 and the date of the survey in 2024 - that might change the number you are calculating by a year or two.

Yes, I think that you are trying to apply a definition of generation that cannot be used to define what you are looking for. Generations for families are specific for each family and need to be traced back by a family tree. There is no one size fits all definition of generation in this sense, since it depends on the specific family dynamics throughout its history.

A line of your family going back10 generations might extend to 1741 (the year your great-g-g-g-g-etc mother was born) while 10 generations back in my family might extend only as far back as 1757. Do this with a few thousand families, and you might find the median year is 1750. So the useful figure in this hypothetical is 27.3 (2023 - 1750 = 273, divided by 10.) You’d probably have to limit it more tightly than just picking “2023” out of the air (something like “everyone’s average age when the 11th generation was born”) but you get the idea.

There is a definite finite number out there of the length of an average generation, and I’m positing that it changes from century to century, from country to country, from culture to culture. I’m asking if anyone has done such a study.

Put another way, I could run a poll of Dopers asking them, if they’re sure they’re finishing procreating, how old they were when each of their children were born. If we got a large enough number of participants, we could approximate what a generation is among the denizens of the Straight Dope, right?

And we could run another poll, asking people to do the same but for their parents. And then another one for their grandparents. If we get large enough numbers of participants, we’ll end up with some fairly stable numbers. Your family may be an outlier, or it may be right in the center, but there will be a number that applies to Dopers across the board.

Extend the SD polling to a much larger group, and put some controls on it so your input is more reliable, and you’ll get a definite number that (I’m guessing) will not differ very much if you conduct another poll with different participants next year.

You could explore some of the MANY research studies done on ‘Changing age of mother at birth’, which provides properly done demographic studies. This will at least cover some of your point.

A taster (referring to Australia - the US will be different):

Average maternal age has risen for both first-time mothers (from 28.4 years in 2011 to 29.7 in 2021) and those who have given birth previously (from 31.3 years in 2011 to 32.2 in 2021) . The* highest proportion of mothers were aged between 30 and 34 (more than one-third (38%) of all mothers).*

Another [US] study says average age of first birth was 30.3 for college-educated women, but 23.8. Their life-time average age at birth for all their kids will of course heavily overlap and have a closer mean, but it highlights the point that ‘age at birth’ is highly socially contextual, approaching a decade on this variable.

Most of this data sits for the past 30 years (a medical generation in effect), but going back a century or into non-western and wealthy areas the shift will be enormous.

Here’s a good, simple trend line for the U.K. that dates back to 1938. in 1944 the average age of mothers was 29.3. From then on the age went down steadily until 1974, when it bottomed out at 26.4. Then it started climbing back, reaching 30.9 in 2021, an all-time high.

10 generations gets me back to 1630.

Wow. Depending on how you’re counting, that’s nearly 40 years per generation. Wow.

Now you’re making me wonder if I counted wrong. If I did, I’m still only off by one (and note, you’re not counting from the year I was born, you’re counting from today, which adds 50 some years to the process)

After we on the Dope come up with the definitive definition, how are we going to get anyone else to use it?

My dad was born in 1906. His mother died in the 1919 Flu epidemic. His first child died in 1935.
My other sister died in the 2020 Covid pandemic. Where do we fit the concept of ‘generations’ into this real-life narrative?