I'll be glad to try.
In my presentation I mentioned the threshold for the top rate, but I also mentioned stretching out the threshold levels for the other brackets. I think that would have to be part of the package, yes. Any politically astute budget that raised one would have to deal with the others as well, not only for political reasons, but because it would also move many taxpayers who are not currently in the top bracket into lower brackets, without explicitly cutting the rates on the various brackets.
On revenue, yes, there would be revenue costs. The most expensive threshold to raise is the bottom threshold, because all taxpayers bear that. We have been raising that bottom bracket beyond inflation in the last budget or two. It becomes less costly as you move thresholds for higher brackets, per dollar of move in the bracket. Yes, there would be significant budgetary impact. Finance people and your committee have the models to crank out the numbers for any conceivable change you might wish to explore.