It's a forgivable impression until you examine what Greens supporters actually think. Asked to rate issues in order of importance in an Essential Media poll in January, more Greens rated economic management No.1 than protecting the environment. The gap was closer among Greens voters than other voters, but the point is there was a difference: Greens put the economy No.1. Polled in November about a specific issue - regulation of the banks - Greens voters were on every measure more closer to economic orthodoxy than Labor voters. Asked if banks should be restricted to lifting rates only in line with the Reserve Bank, 87 per cent of Labor voters said yes. Even among Coalition voters 82 per cent said yes. But among Greens voters, the result was 73 per cent, suggesting they are more likely to have studied economics. Asked if bank fees should be kept to the cost of providing the service, 93 per cent of Labor and 93 per cent of Coalition voters agreed. Only 90 per cent of Greens voters thought so. Asked about a cap on bank salaries, 88 per cent of Labor voters were for it. Coalition voters were less keen, at 83 per cent. In the middle, less in favour of hobbling the market than Labor voters, although more so than Coalition voters, were the Greens at 86 per cent. The views of Greens supporters are not outside the mainstream, except in that they are likely to be more in touch with orthodox economics than the mainstream.

Greens voters are far more likely than either Labor or the Coalition to support higher taxes on mining profits, a view in line with the International Monetary Fund, the Henry review and the Treasury. They are less likely than the majors to be fussed about a return to a budget surplus by exactly 2012-13 (as are orthodox economists), although, interestingly, slightly keener than Labor voters on spending cuts in the budget to come. They are more likely than Labor voters to act against self-interest. Only 17 per cent of Labor voters would accept a tax on products bought online from overseas but 19 per cent of Greens voters would. And they know more. An astonishing 10 per cent of Labor and 12 per cent of Coalition voters are deluded enough to think half our migration intake is boat people. Only 6 per cent of Greens voters think so.

They are accepting of the mainstream scientific position on climate change - that it is happening and caused by human activity; far more accepting than supporters of either Labor or the Coalition. And they believe market mechanisms rather than regulations are the best way to get emissions down. Their tax policies echo those of the Henry tax review. Tax breaks for high-income earners would go, fringe benefits tax concessions that encourage the needless driving of cars would be scrapped, and capital gains would no longer be tax-preferred over other returns from saving. All income received would be taxed at the standard rate and the scales would be rejigged to remove the high effective rates faced by Australians trying to get off welfare. Henry would do this by flattening the scales and making the first $25,000 earned tax free. The Greens aren't so sure about that, but neither are Labor or the Coalition. The point is that on nearly every area where the Greens diverge from Henry, the Coalition and Labor do too.

On most of the areas where the Coalition and Labor are reluctant to embrace Henry, the Greens are keen to. The big parties won't touch the private health insurance rebate. The Greens would kill it, as would Henry. The big parties aren't attracted to a death duty. The Henry review is, and the Greens would bring it in with a threshold of $5 million and an exemption for the family home, farm and small business. The big parties are grudging about making the mammoth superannuation tax concessions more progressive. Henry isn't, and the Greens would do it, after a ''full review''. This isn't an argument in favour of Greens policies, although as it happens I find them attractive. It is an argument that they fit within the economic mainstream. They are coherent, readily available on the web, and far more than a grab-bag from a ''party of protest'' that likes to sit ''under the tree and weave baskets with no jobs''. If the Greens have got it wrong on economics, then so have the economics textbooks they seem to have read and so too has Ken Henry.

Their real position is important because that is what will determine what gets passed into law in the two to three years ahead, not the misleading dumbed-down characterisations of a Prime Minister and ministers who should know better. Peter Martin is economics correspondent Twitter: @1petermartin