I don't understand poverty statistics. With this news, the UK now has more people living in poverty than India (16% vs 22%?). If it is valuable to judge poverty on relative income, you would think the rational course of action would be mass immigration from the UK to India but that is clearly not the case.
Ultimately, the purpose of that statistic for the state to be able to tell whether its policies are working. The state, therefore, must construct measures that show progress when it makes progress and show regress when it makes errors. A measure that ultimately shows 0 progress even when real progress is made, is not that useful to the state.
A data nerd may want to normalize definitions (I certainly do and the MMR and IMR measurements are ones I find particularly annoying) but ultimately a state measures for its own purposes and not mine.