Measuring poverty over time

The conceptualisation and measurement of poverty has been the subject of intense study for more than a century. The adoption of the Millennium Development Goals (MDGs) in 2000 gave additional stimulus to these longstanding efforts, this time at the global level, and the progress made towards reducing world poverty is encouraging. World Bank estimates, for example, suggest that the percentage of the population in the developing world living below $1.25 a day declined from 52% in 1981 to 22% in 2008, bringing the number of people living below $1.25 a day down from 1.94 billion in 1981 to 1.29 billion in 2008. These numbers are now based on over 850 household surveys for almost 130 developing countries, representing 90% of the population of the developing world, compared with only 22 surveys for 22 countries when the first such estimates were reported in the 1990 World Development Report [9]. Alongside improvements to the quantity and quality of data, there have also been significant advances in conceptualizing and measuring poverty. One noticeable shift is the movement away from an exclusive focus on consumption-poverty, with attention now often also given to non-income dimensions of well-being, such as literacy achievements, nutritional and health status and individual empowerment. This has led to lengthy debate concerning the way in which various dimensions of well-being are best combined into a single multi-dimensional poverty measure: see, for example, the discussion in the Journal of Economic Inequality 2011, Volumes 9–2 and 9–3, regarding the weights assigned to shortfalls across each of these dimensions, and the question of complementarity as well as substitutability across the indicators of well-being.