12.1. Valid, reliable, timely, culturally relevant and internationally comparable data form the basis for policy and programme development, implementation, monitoring and evaluation. While there have been marked improvements in the availability of population and related development data following important advances made during the past two decades in the methodologies and technology for data collection and analysis, many gaps remain with regard to the quality and coverage of baseline information, including vital data on births and deaths, as well as the continuity of data sets over time. Gender and ethnicity-specific information, which is needed to enhance and monitor the sensitivity of development policies and programmes, is still insufficient in many areas. Measurement of migration, particularly at the regional and international levels, is also among the areas least valid and least adequately covered. As a matter of principle, individuals, organizations and developing countries should have access, on a no-cost basis, to the data and findings based on research carried out in their own countries, including those maintained by other countries and international agencies.