If immigration and emigration are ignored, what is the verbal equation for change in population size during a time interval?

A verbal formula for change in population over a time
period (disregarding immigration and emigration) would be as
follows:

Population Change equals Number of Live Births
minus Number of Deaths (the births and deaths occurring in the stated time
period).

If births outnumber deaths, the population change
is a gain.  If deaths outnumber births, the change is negative, or a
loss.

Population growth rate
is defined as the percentage of population change over time, expressed as a fraction of
the initial population.

Example of Population Growth Rate
Calculation:

World Population in 2006 = 6.7
Billion

World Population in 2011 = 7.0
Billion

Population Growth Rate = (7.0 – 6.7)/ 6.7  x 100 =
 .3/6.7 x 100 = 4.47% (in 5 years) = .89% per year

As an
interesting aside:  the world population is projected to reach 7 billion by this coming
Halloween!