The Grattan Institute has just released a report suggesting that the government should get more revenue from the GST, either by broadening the base to include food, health and education (yielding an extra $17 billion) or by raising the rate to 15% (yielding an extra $27 billion). As you’d expect from Grattan, the analysis is sound and careful. As long as you accept the standard framing of the tax reform debate, in terms of the need to shift from direct to indirect taxation, it is reasonably convincing.

Grattan suggests using 30% of the extra revenue to increase welfare payments and 30% in cutting the bottom two tax rates, thereby compensating low-income earners. The overview concludes:

“Around 40 per cent of the additional revenue from a higher GST would be left over after welfare increases and tax cuts. At least some will need to go to state governments to help them address their looming hospital funding gap, as the price for their support of the change. This would leave a little — but not much — to reduce the Commonwealth’s budget deficit, or to pay for other tax cuts that promote economic growth.”

Is that enough to sell the package? I can’t imagine the states going along with a deal like this for less than 20% of the total extra revenue, which implies the Commonwealth is left with 20%, somewhere between $3.5 and $5.5 billion. From a political viewpoint, it’s hard to see this being worth the effort for the Turnbull government, especially with no guarantee of success.

As a comparison, the fringe benefits tax concession for motor vehicles, reinstated by Tony Abbott, costs the budget around $1.5 billion. Exemptions for non-profits, which have been comprehensively rorted, cost at least as much. Add in a few “rats and mice” concessions, and the federal government would have as much as it could get, in net terms, from the Grattan package. (Getting rid of the non-profit concession would probably require some compensating expenditure, but the same is true of the health and education concessions under the GST.)

That’s before we get to the elephants: superannuation concessions (also supported by the Grattan report), corporate tax avoidance, land tax and higher income taxes for (say) the top 5% of income earners (reflecting elite opinion, the Grattan report suggests cutting these rates). All of these are hard, but not obviously harder than the GST.

So why is GST reform at the top of the government’s list? The answer is simple enough. The advocates of reform haven’t had a new idea, on taxation or anything else, in 30 years. They didn’t get the GST out of Keating’s Tax Summit in 1984 and they didn’t get the version they wanted from Howard and Costello in 2000. So, the same old idea keeps on coming up.