In the developed world the importance of evidence-based policy is increasingly recognised. Panel studies – a long-term study design where a cross-sectional sample of units is selected and surveyed at regular intervals – are being used to gather information about the same people or...

Many developing countries are trying to improve the routine collection of health information by strengthening surveys, censuses, and registration systems. At the international level, too, efforts are underway to provide information on health and health interventions, including statistical...