As a tangent, poverty line definitions vary by country, in Australia, for example, earning less than half the median wage is considered below the Australian poverty line.
Worth keeping in mind when doing any apples V oranges country by country comparisons of population percentages in poverty.
* AU: https://povertyandinequality.acoss.org.au/poverty/
* UK: https://en.wikipedia.org/wiki/Poverty_in_the_United_Kingdom
* US: https://en.wikipedia.org/wiki/Poverty_thresholds_(United_Sta...
As I understand it, that's a fairly common definition for relative poverty (either that or 60%) though of course you're still right that it's best to confirm both the threshold the methodology is the same (or use an explicitly international comparison that covers both/all compared countries in the same work, such as those produced by the OECD or similar bodies).