I don’t remember exactly, but some relative poverty lines start at 60% of median household income.

• £700 / (£32,400 * .6 / 12) ≈ .43, thus 43% of monthly income for a poor household in the UK
• $700 / ($74,580 * .6 / 12) ≈ .19, thus 19% of monthly income for a poor household in the US

I hope median household income is netto, otherwise this is skewed.