方法对比

	Poverty Gap Index	Foster-Greer-Thorbecke Index
领域	经济学	经济学
方法族	Process / pipeline	Process / pipeline
起源年份	1984	1984
提出者	James Foster, Joel Greer & Erik Thorbecke (FGT alpha = 1)	James Foster, Joel Greer & Erik Thorbecke
类型	Money-metric poverty depth measure	Parametric class of poverty measures
开创性文献	Foster, J., Greer, J., & Thorbecke, E. (1984). A class of decomposable poverty measures. Econometrica, 52(3), 761–766.	Foster, J., Greer, J., & Thorbecke, E. (1984). A class of decomposable poverty measures. Econometrica, 52(3), 761–766.
别名	Poverty Gap Ratio, Income Gap Measure, Mean Normalized Shortfall, Depth of Poverty	FGT Index, FGT Poverty Measures, P-alpha Poverty Index, Foster-Greer-Thorbecke Poverty Measure
相关	3	4
摘要	The poverty gap index is the member of the Foster-Greer-Thorbecke family at alpha = 1 and the standard money-metric measure of the depth of poverty. Where the headcount ratio merely counts who is poor, the poverty gap averages how far the poor fall below the poverty line, expressed as a fraction of that line and spread over the whole population. It can be read as the per-capita resource shortfall — the share of the poverty line, per person, that perfect targeting would need to transfer to eliminate poverty — making it the natural complement to the headcount when judging the cost and intensity of poverty.	The Foster-Greer-Thorbecke (FGT) index is a parametric class of poverty measures introduced by James Foster, Joel Greer, and Erik Thorbecke in 1984 that became the workhorse of applied poverty analysis. A single parameter alpha tunes how much weight the measure places on the depth and distribution of poverty: alpha = 0 gives the headcount ratio (the share of people below the poverty line), alpha = 1 gives the poverty gap (the average normalized shortfall), and alpha = 2 gives poverty severity (which weights larger shortfalls more heavily). Its defining virtue is additive decomposability — total poverty is the population-weighted sum of subgroup poverty — which makes it ideal for profiling poverty across regions, sectors, and demographic groups.