Mark Steyn explores this in the excellent book America Alone. It's persuasive, and the numbers are stark. Going off the Total Fertility Rate (TFR) measure, each woman needs to have at least 2.1 babies to maintain a steady population. Looking at a list of countries by TFR the EU average is 1.59 with Greece at 1.3, Germany and Italy at 1.4. Britain a relatively healthy 1.9, but still pointing towards long term population decline. By contrast Niger leads the world in baby production with a TFR of 7.6, beating Somalia (6.6) quite comfortably with Mali and Chad tied for 3rd on 6.3.
The list goes on in that fashion. By these figures the world is becoming more African and more Islamic at a fairly alarming rate while Europe is failing to produce enough people. So Africa and the Middle East have too many people, Europe has too few. Surely the answer is obvious, and the huge cultural shift that will come of importing over a million Muslims a year is just something we'll have to learn to live with?
No. Like most attempts to use broad and simplistic statistics to explain complex problems this is hugely misleading.
A very unscientific walk up a European street will show you this. Many couples do have 2 or 3 children. Some have more. Some stop at 1. The vast majority of these will live to be adults and a good deal of them will have children of their own. There are still Europeans being born.
According to the BBC, who would love us to believe the population decline narrative, there were 698,512 live births in 2013, and 26.5% of those were to mothers born outside the UK. Hugely significant, but not quite panic stations. 73.5% of 698,512 is 513,406 British babies born in England and Wales that year. With a life expectancy of 81.5 years that gives a steady state population of 41.8 million, compared to the current 56 million. A decline, but hardly a death spiral.
In fact with a fairly crowded country with a seemingly religious aversion to building new houses or roads, a 30% decline in population might not be a bad thing. Yes we would have to deal with the pension and social security problem, but we will have to deal with those anyway. There is really no need to add a load of aggressive Muslims into the equation.
Steyn's explanation is that the post-religious, rudderless, secular liberal societies run by self-indulgent baby boomers and passed on to their eternally adolescent offspring are simply not motivated to have children. Perhaps a better explanation is that as people have more control over their reproduction, something really quite recent in demographic terms, certain groups have shown themselves to be a sort of evolutionary offshoot. This still ties in with the selfish boomers hypothesis but recognises the fact that they are only one component of the population.
Of course whatever the explanation, importing the wrong sort of people to make a dysfunctional system work is sheer insanity. If the alternative was extinction then it probably wouldn't really matter, but the actual alternative appears to be a country of around 40-45 million people, the sort of levels we had in the 1970s. Only they would be better housed and wealthier. They might have to pay higher taxes for a few years and they might have to make their own pension provisions. But they wouldn't have to live with the pleasures of mass third world immigration and creeping Islamisation.
Sounds good to me.