The natural increase rate tells us how the population of a region is growing. It is calculated by subtracting the death rate from the birth rate.
Natural Increase Rate = Birth Rate - Death Rate
If the natural increase rate is positive, it tells us that the death rate is lower than the birth rate and the population is growing. If the natural increase rate is negative, it tells us that the death rate is higher than the birth rate and the population is declining. However, understand that this statistic does not take immigration into consideration.
I hope this helps!