How can one accurately keep up with the population with birth and death statistical data?

Let's say statistics are "every year 5000 people die in car accidents + 1000/yr die from breast cancer.etc. How would one keep track off all this data? accurate is this data? How do we really know how many people every year die from something? I nderstand statistical data is just used for referrence, but then why do so many companies, and such use it to "prove" their point?
How off do you think the "supposed Earth's population is? What would one have to do to start a collection of data on the subject? As far as keeping track of each countries' population? Is there a "World Birth and Death Data" site somewhere?
Thx for all the help .

Scientist have already calculated that in order for any country to keep the population exactly the way it is now, each woman in that nation needs to have approx 2.2 children.

Europe is changing because most of the countries are under 2 the Muslim immigrants are at about 5 do the math. the US is about at 2.1 and that's only because of immigrants from Mexico. I hope this was able to help.
I am sure that for birth, they can use birth certificates to track it.
When someone dies, I believe there must be some kind of record filed (most likely from the coroner). It may even be possible to upload this information into a database.

The accuracy would vary from country to country. The total world population is an educated guess, since a lot of underdeveloped countries do not keep this kind of data (at least not in a sophisticated form).

Go to the CIA World Factbook website:

The answers post by the user, for information only, does not guarantee the right.

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