Gross Reproduction Rate Calculation

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Gross Reproduction Rate (GRR) Calculator

Demographic Analysis Tool for Population Growth Potential

Avg. number of children per woman.
Standard is approx 105 males per 100 females.

Calculation Result

Gross Reproduction Rate (GRR): 0.00

What is the Gross Reproduction Rate (GRR)?

The Gross Reproduction Rate (GRR) is a demographic metric that measures the average number of daughters a woman (or a cohort of women) would have if she survived through her entire reproductive lifespan (usually ages 15 to 49) and experienced the age-specific fertility rates observed in a particular year.

Unlike the Total Fertility Rate (TFR), which counts all live births, the GRR specifically focuses on female offspring. This is because female births are the primary drivers of future population replacement and growth.

The GRR Formula

The simplest way to calculate the GRR when the Total Fertility Rate and the sex ratio at birth are known is:

GRR = TFR × (100 / (100 + Sex Ratio at Birth))

Where "Sex Ratio at Birth" is usually expressed as the number of male births per 100 female births.

GRR vs. NRR (Net Reproduction Rate)

While the Gross Reproduction Rate is a useful measure of fertility potential, it has one major limitation: it assumes that all women survive from birth until the end of their childbearing years.

  • GRR: Measures fertility potential without considering mortality.
  • NRR: Adjusts the GRR to account for the probability of a woman dying before she reaches or completes her reproductive years.

Practical Example of GRR Calculation

Suppose a country has a Total Fertility Rate (TFR) of 2.5 and a sex ratio at birth of 106 males for every 100 females.

  1. Determine the proportion of female births: 100 / (100 + 106) = 100 / 206 ≈ 0.4854.
  2. Multiply the TFR by this proportion: 2.5 × 0.4854 = 1.2135.
  3. The GRR is 1.21. This means, on average, each woman is expected to have 1.21 daughters during her lifetime.

Interpreting the Results

  • GRR > 1.0: Each woman is being replaced by more than one daughter. The population has the potential to grow, assuming mortality rates are low.
  • GRR = 1.0: Each woman is replaced by exactly one daughter. This is roughly "replacement level" fertility (though NRR is a better indicator of actual replacement).
  • GRR < 1.0: Each woman is being replaced by fewer than one daughter. Without significant changes in fertility or high immigration, the population will eventually decline.
function calculateGRR() { var tfr = parseFloat(document.getElementById('tfr_input').value); var ratio = parseFloat(document.getElementById('sex_ratio_input').value); var resultBox = document.getElementById('grr_result_box'); var grrValue = document.getElementById('grr_value'); var interpretation = document.getElementById('grr_interpretation'); if (isNaN(tfr) || isNaN(ratio) || tfr <= 0 || ratio 1.1) { text = "Interpretation: This indicates a high potential for population growth, as women are producing significantly more than one daughter on average."; } else if (grr >= 0.95 && grr <= 1.1) { text = "Interpretation: This is near the replacement level. If mortality rates are low, the population size should remain relatively stable over time."; } else { text = "Interpretation: This is below replacement level. Unless balanced by high survival rates or immigration, the population potential is declining."; } interpretation.innerHTML = text; }

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