If Congress Voted Every Few Years to Redefine Completely What

If Congress voted every few years to redefine completely what poverty means,

A) it will be useful to have a poverty line whose basic definition changes a lot.
B) then it will set two poverty lines that it applies to welfare and the near-poor.
C) then a substantial share of the U.S. population will subsist in dire poverty.
D) then it would be difficult to compare poverty rates over time.