This chart above is 2 years old but elucidates this Long term pattern.
looking at just US households debt/GDP:
Credit growth relative to GDP has been modest at best since the peak in 2007. This is the one factor that could explain why global financial market has been performed poorly and USD strong until early 2016-2017. Global growth has been meek because it was done using mainly existing savings, not new credit, until 2016.
This is a list of the highest household debt nations: (this is the make sure none of these top 20 countries are in our ETF portfolio)