I would add that if you're comparing the $29 billion to the $17 billion, it's roughly a $12-billion difference. There is $6 billion of that which actually relates to a contingency reserve that was included in the $29 billion. That was a forecast that was done in March 2016, at a time when the economy was weak. Oil prices were around $25, if I go from memory. Of course, the economy recovered quite nicely, and has recovered quite nicely, so the combination of not needing that amount of contingency, plus a stronger economy as things evolved, meant that the overall deficit came in much lower than projected.
On October 17th, 2017. See this statement in context.