I do place some credibility in things Costello says, because it was he, after all, who laughed when asked about Tony Abbott's economics skills.
He was clearly correct on that matter, so he does have some credibility, even if he was extremely lazy and sadly lacking in proactivity as a treasurer.
When he could see the end of the unsustainable boom on which he depended, was coming to an end, he simply stood there in wonderment and said, "the storm clouds are gathering".....and didn't offer one ounce of suggestions on how to deal with the storm.
Luckily we had Labor who dealt with it very effectively, and brought praise from economists worldwide.
