Use this fertility measure when the births, women at risk, parity categories, and observation period follow the definition required by the selected method.

Women by parity

Number of women at each parity starting with parity zero.

Percent

Percentage of women in each parity class.

Period and cohort fertility answer different questions. Survey recall, parity truncation, changing age patterns, union definitions, and mismatched exposure populations can materially change the result.

Pair period fertility with cohort measures, parity distributions, or wanted-fertility indicators when available. These complementary views separate timing changes from completed family size and stated preferences.

• Birth Interval Median By Parity Calculator

  Compute the median length of birth intervals in months for a set of closed intervals observed at a given parity transition.

• Parity Progression Ratio PPR Calculator

  Compute Brass parity progression ratios a(i), the share of women who have reached parity i and go on to parity i+1 or higher.

• Primary Infecundity Percent Lookup

  Compute the percentage of women with primary infecundity and classify it as low below 2.5 percent, moderate from 2.5 to 5 percent, or elevated above 5 percent.