Sunday, October 3, 2010

Demographics: all about rates and more

In here, there will be mentioned several rates, such as CBR and CDR, for example.

Crude Birth Rate
The Crude Birth Rate (CBR) includes the number of births per 1000 individuals. So, the formula for this is:

CBR = (Number of births / population size) x 1000

The CBR in the world is 20.3 per 1000 per year.


Crude Death Rate
The Crude Death Rate (CDR) includes the number of death per 1000 individuals. The formula for this is:

CDR = (Numberof deaths / poplation size) x 1000

The CDR in the world is 9.6 pero 1000 pero year.


Natural Increase Rate
To know the Natural Increase Rate (NIR), it is important to know the Crude Birth Rate and the Crude Death Rate, The formula for the Natural Increase Rate is:

NIR = (CBR - CDR) / 10

It is important to say that NIR gives a percentage.


Doubling time
Last semester we saw doubling time, but we didn't saw it in a clear form. Now, we saw it in class, and with this we know that doubling time is the time in years that it takes a population to double its size. The doubling time formula is:

Doubling time = 70 / NIR

This do not considers immigration nor emigration.

Total Fertility Rate
Now, continuing with rates, we have the Total Fertility Rates (TFR) which is the average number of children that each woman has over her lifetime. This one shows the potential for population change in a country.

A Total Fertility Rate that is less than 2.0 it results in population increase. But if the Total Fertility Rate is more than 2.0 it esults in population decrease.

Factors affecting species impact
Factors affecting species impact on the environment (without counting population size) are:
  • Wealth, including its distribution.
  • Resource need
  • Resource desire

No comments:

Post a Comment