The total fertility rate in a specific year is defined as the total number of children that would be born to each woman if she were to live to the end of her child-bearing years and give birth to children in alignment with the prevailing age-specific fertility rates. It is calculated by totalling the age-specific fertility rates as defined over five-year intervals. Assuming no net migration and unchanged mortality, a total fertility rate of 2.1 children per woman ensures a broadly stable population. Together with mortality and migration, fertility is an element of population growth, reflecting both the causes and effects of economic and social developments. The reasons for the dramatic decline in birth rates during the past few decades include postponed family formation and child-bearing and a decrease in desired family sizes. This indicator is measured in children per woman.

[–] Dave 2 points 9 months ago (1 children)

Yeah I don't know. Like I get it at a conceptual level.

It basically says that they work out the fertility rate by dividing the number of women by the number of babies. They say they do it in 5 year blocks, I guess this accounts for say lots of kids or lots of old women skewing the numbers when they don't have babies.

As for why we have 38,000 deaths and 59,000 births and this is below the replacement rate, I start to feel like I understand but then decide I don't. The best answer I've found is a suggestion that births per women below 2.1 doesn't necessarily mean a shrinking population, because of the distribution of women of various ages may mean many women of childbearing age (say, through immigration) can cause the population to grow despite births per women being below 2.1.

[–] eagleeyedtiger 2 points 9 months ago (1 children)

It’s too late and I can’t wrap my head around it. Is there some effect from what the deaths and births are? As in it’s not necessarily old people dying and not all births are female which would then further impact the fertility rate?

I understand that the 2.1 replacement rate needed is assuming no migration. There will almost always be migration though.

I think I need to sleep and stop trying to understand this

[–] exocrinous@lemm.ee 2 points 9 months ago (1 children)

Low fertility rates mean the death rate will be higher than the birth rate in the future. But not necessarily right now.

Imagine I build 100 robots, who will each live precisely 100 years. One robot chooses to build a replacement for itself, the rest do not. For 100 years, the death rate will be 0, and the birth rate will be 1. So more births than deaths. But the fertility rate is 0.01, so in 100 years the first generation will all die. Today the birth rate is higher, but low fertility means it'll be lower eventually.

[–] Dave 1 points 9 months ago

Thanks! Like @eagleeyedtiger@lemmy.nz, I think I just needed some sleep.