structural:reformatting
Variability

Poverty levels are snapshot pictures in time that omits the transitional dynamics between levels. Mobility statistics supply additional information about the fraction who leave the poverty level. For example, one study finds that in a sixteen-year period (1975 to 1991 in the US) only 5% of those in the lower fifth of the income level were still at that level, while 95% transitioned to a higher income category. Poverty levels can remain the same while those who rise out of poverty are replaced by others. The transient poor and chronic poor differ in each society. In a nine-year period ending in 2005 for the US, 50% of the poorest quintile transitioned to a higher quintile.