Once you have determined the types of contraceptive methods that your program will offer to clients, you need to estimate the number of clients who will use each method in a given time period, usually a year. Although it is not possible to predict changes in client demand or interruptions in supply accurately, a careful analysis of past supply and use patterns will enable you to request appropriate amounts of each type of contraceptive.

When you introduce a new method, you will have to plan for the changes in client preference that will result. For example, if you decide to increase the range of methods available to include a new contraceptive such as a contraceptive implant, you must try to anticipate changes in contraceptive preferences as clients switch from their current method to an implant or new clients come to the clinic requesting the contraceptive implant.

Contraceptive needs should be forecast at least annually and reviewed quarterly. Whenever there is new information that changes assumptions about client preferences, you should conduct a thorough review of your forecasts.

You can estimate contraceptive needs by using population-based, distribution-based, or service-based methods, or a combination of these. They all have their advantages and disadvantages.

Population-based estimates uses demographic information to estimate the number of clients the program intends to serve and the anticipated demand for each type of contraceptive method. To perform a population-based estimate, you need to determine:

• The population of the area to be served
• The percentage of the population who may request contraception
• The percentage of people using each type of contraceptive

This information is often available from national demographic or health and family planning surveys. Population-based estimates are based on very broad statistical data which may be inaccurate when applied to smaller areas such as regions or districts. The advantage of using population-based estimates is that they are easy and quick if the data are available. Some disadvantages are that they are difficult to distinguish what proportion of the contraceptives will be provided by the private sector and what proportion by the public sector, and that population-based estimates do not take into account the use of condoms for purposes other than family planning, such as controlling the spread of sexually transmitted diseases and AIDS.

This approach should generally be used only at the earliest stages of a program. As patterns emerge in the actual amounts of contraceptives dispensed, these will become a more accurate basis for making estimates.

Distribution-based estimates use inventory data to determine the number and types of contraceptives that have been distributed in the program over a specified period of time. Ideally, this is based on actual quantities dispensed to users. However, when this information cannot be obtained from an appropriate service statistics system or family planning logistics management information system, data on contraceptive distribution can be used for forecasting future requirements.

Service-based estimates are made by analyzing records at the service delivery level and projecting the number of clients that a program expects to serve. To perform a service-based estimate for an existing program, collect data from clinic records on how many clients being served, what contraceptives they are receiving, and in what quantity. Adjust these numbers for any increase in services you expect to provide or any changes in client preference that you anticipate.

The greatest advantage of the service-based method is that it uses data already generated by the program. The disadvantage of this method is that the data may be unreliable due to poor or inaccurate reporting.

Tools and Techniques - Guidelines for Estimation