Primary sources for household debt-to-GDP (households + NPISH):
1) BIS Data Portal (Credit to the non-financial sector): https://data.bis.org/
2) BIS Total credit statistics overview: https://www.bis.org/statistics/totcredit.htm
3) BIS long series / break adjustments note (methodology): https://www.bis.org/publ/qtrpdf/r_qt1303h.htm

Cross-check / complementary sources (coverage varies):
4) OECD household debt: https://data.oecd.org/hha/household-debt.htm
5) IMF (context / alternative debt datasets): https://www.imf.org/

Snapshot used in these assets: 2025-Q2 (as labeled in the tables).