The Demographic Method: A Step-by-Step Guide

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Use when: a programme serves a defined population, or a new product (such as a new vaccine) has no consumption history.

Setting up the assumptions

• Population: census or projection, with source year and growth rate.
• Target group: e.g. surviving infants, women of reproductive age (%).
• Coverage: realistic, based on comparable products rather than targets alone.
• Need per person: schedule doses or supplies per user per year.
• Wastage: expected rate, depending on vial and session size.
• Safety stock: often higher in the first year of an introduction.

Procedure

1. Target population = total population × target group share.
2. People reached = target population × coverage.
3. Quantity = people reached × need per person.
4. Apply the wastage factor: ÷ (1 − wastage rate).
5. Add safety stock; subtract stock on hand and on order.
6. Convert to vials or packs and cost.

Worked example: new vaccine

A district of 400,000 people introduces a two-dose childhood vaccine.

Assumptions: surviving infants 3.2%; coverage 85% (as for an existing vaccine at the same visits); wastage 10%; first-year safety stock 25%; no existing stock; 10-dose vials.

Step	Calculation	Result
Target population	400,000 × 3.2%	12,800 infants
Infants vaccinated	12,800 × 85%	10,880 infants
Doses administered	10,880 × 2	21,760 doses
Including wastage	21,760 ÷ 0.90	24,178 doses
Safety stock	24,178 × 25%	6,045 doses
Total	24,178 + 6,045	30,223 doses
Vials	30,223 ÷ 10, rounded up	3,023 vials

Worked example: oral contraceptive pills

Step	Calculation	Result
Women of reproductive age	400,000 × 22%	88,000 women
Modern method users	88,000 × 30%	26,400 users
Pill users (method mix)	26,400 × 20%	5,280 users
Annual need	5,280 × 13 cycles	68,640 cycles

Key considerations

• Census data may be outdated; account for growth and migration.
• Policy targets often exceed achieved coverage.
• Match the target group to the programme.
• Base wastage on observed rates.
• Replace assumptions with consumption data once available.

Acknowledgement and further learning

Based on the online course on forecasting and quantifying medicines and health products offered by i+academy; all credit belongs to the course and its facilitators. For a fuller understanding, enrol in the course on i+academy.

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Other guides in this series: Consumption method · Morbidity method · Other methods