Keen had previously claimed Australian housing would decrease by 40% in
real terms over a decade or so. Keen was ambushed at a news conference by Robertson, who out of the blue challenged him on the claim, offered him the bet, but threw in the "within 1 year rider", the "within 1 year" appeared to be agreed to unwittingly by Keen.
Here are his own words:
Kosciuszko Walk. What was unpredictable was the change in government policy (First Home Buyers Grant) to prop up the market. That antidote is now wearing off and housing is again on the descent, merely delayed, not fixed by the policy.
As for being the a joke, he was one of the few economists who called the crash in 08, despite Glen Stevens claiming "nobody could have predicted it", well, he did, years before, as did the Austrian school (Keen is post-Keynesian).