(Image: AAP/James Gourley)

The thing about events which are unprecedented, is that no one knows what the hell will happen.

It's human nature to look through a positive lens. That’s why sharemarkets and property markets have largely gone up for two generations since 1983 (with just a few blips in 1987, 1992 and 2008).

But this period of unprecedented expansion has coincided with a massive increase in debt around the world (but especially in the US, Europe and China). It’s been so long since we’ve seen a protracted downturn that it seems like no one knows what to expect. Forty years of a relentlessly positive trajectory will do that.