How do I calculate the future racial make up of England?

Question

Native British reproduce at 1.24 kids per woman and foreigners reproduce at 4.1 kids per woman. To sustain the population both groups have to reproduce at 2.1 kids per woman. Right now native British is 90% and foreigners are 10%. How do I calculate the racial make up for the year 2106?

Answer 1

You are missing 6 pieces of information needed to solve this problem:

1) What is the ratio of men to women in England
2) What is the average life span of Women in England
3) At what rate do foreigners become native through inter marriage?
4) at what rate do these birth rates change through the years.
5) The death rate during the years
6) What is the immigration rate during these years

Lets make some assumptions

1) There is one man for every woman in England. (not exactly true)
2) lets say the lifespan in years for the average Englishwoman is
60 years
3) Natives and foreigners despise each other and there no inter marriages
4) The birthrates remain absolutely constant through the years in question
5) The death rate is .5% per year for both groups
6) They close the borders

If 1 represents the entire population of England now . Then .5 is the number of women. .9 X .5 = .45 is the number of native women, and .1 x .5 = .05 is the number of foreign women.

English women produce 1.24/60 children each in the first year so the native population after the first year is (1- .005) X (.9 + ,.45X1.24/60)

Similarly foreign women produce 4.1/60 children in the first year so the foreign population after the first year is (1-.005) X(.1+.05x4.1/60.)

You can do this recursively for each year, so that you find the total natives and foreigners at year 2106. I leave the math of doing the recursion as a formula to you,

Once you have these answers, the ratio of natives to foreigners is simple: The total population is the total of natives and foreigners, and the ratio of foreigners is the total foreigners divided by the total population. the ratio of natives is the total natives divided by the total population.

Answer 2

In order to make a prediction, many assumptions must be made. Let's assume that the rates of reproduction remain constant in the two groups over the next 100 years. Let's assume that there's no intermarriage between the groups. Let's assume that men and women are each half of the population. Let's assume that both groups have a constant birth and death rate, meaning that both populations experience exponential growth. Let's assume that the average life span in both groups is 70 years and that each individual has a constant probability of dying in each year of his life, and a constant probability of reproducing.

These are some very strong assumptions and certainly they are at best a crude approximation.

Under these assumptions, the death rates in both groups would be the same, at around 1/70 per person per year. The birth rates would be about 1.24/(2 X 70) for British and 4.1/(2 X 70) for foreigners. This translates into a negative growth rate for British of about -(1.24/(2X70) - 1/70) = -.54 percent per year, while for foreigners there would be a positive growth rate of (4.1/(2X70) - 1/70) = 1.5 percent per year. Extrapolating out 100 years, we find the British have shrunk to a little over half their current population, while foreigners have become more than 4 times as large. Brits are still a majority, but not by much. Going out 200 years, the Brits are outnumbered over 6 to 1 by foreigners. Going out 1000 years, the number of Brits is negligible; less than 1 in 70 million is a Brit.

Answer 3

Assume all foreigners are male, so in 2106, native British will still be 90%. Also assume immigration and death rates remain constant. And that both populations wait until age 20 t0 reproduce, and that longevity is identical. Is the child of a British woman and foreign man British? Is British a race?

Answer 4

By knowing at what point the foreigners become native Brits.
Or was that whites only for the Brits and all other colors for the foreigners?? Then you would need additional numbers of each birth rate for each color, or are you lumping all the foreigners under one banner? If so, then back to the original sentence.
...jj

Answer 5

At that rate of reproduction, by 2106, the foreigners will be in the majority.

Answer 6

Too many variables to make anything close to an exact prediction. As one group rises in prosperity, the birth rate decreases, so while the percentages will become closer together, no-one can predict how close.

Answer 7

Chronologically- by multiplying the circumference- times the mass of the volume, in centimeters-taken to the 4th power and dividing the diameter of the posterier-- ---wait, just one minute----no,- uh- hold up--

Answer 8

"Native" British population?
WHAT?
You mean like the Romans?
Or the Celts?
Or Neanderthal?
Or Fairies and Ogres?