Survival Rate

The survival rate is the proportion of individuals in a population who survive from one time period to the next (e.g., year to year or age group to age group).

• For a given time interval:
  \[\text{Survival Rate}=\left(\frac{\text{Number alive at end of period}}{\text{Number alive at start of period}}\right)\]
• The value ranges from 0 to 1 (or 0% to 100%).
• Population growth rate = Birth rate – Death rate.

• Birth rate is the number of births per year (usually per 1,000 people).
• Death rate is the number of deaths per year (usually per 1,000 people).
• Survival rate is a separate concept, focusing on how many in a group survive across a time interval.

Imagine planting 1,000 seeds. After a year, 950 sprout and grow, so those surviving seeds represent a 95% survival rate.

• Survival rate measures what fraction of a group remains alive after a given time.
• Population growth rate, by contrast, calculates if the population is increasing or decreasing, combining births and deaths.