If IQ was the sole determinant, maths professors would all be millionaires. Many successful businesspeople did badly at school.
There is no doubt a new professional 'knowledge' class (lawyers, bankers, etc) has developed. Ironically it's because of world trade, which was supposed to make the world fairer as each society does what its good at. Traditional labourers and manufacturing salaries are declining as overseas labour competes with them. Relatively free movement of goods and capital means local manufacturing decreases, while 'knowledge' intensive roles such as lawyers, accountants, bankers, etc to facilitate that trade increases. Foreign exchange, foreign trade laws, international accounting standard, cross-border M&A, offshore stockmarket listings, multiple-jurisdiction tax, etc. World trade has created massive need for people in these areas, with the result that such people are paid more and more while unskilled labour, which is still plentiful, get paid less and less.
All you can say is that the development of world trade means income distribution is actually getting less fair on a local level. Arguably without world trade, incomes in China would be fairer (though almost everyone would be poor) while in the US or Australia, it would be more like the 50's where more people were employed in manufacturing and generally things were 'fairer'.
The only way you can impose fairness (as Japan managed to do during the decades after the war: even now Japanese pay is relatively fair in that income ranges are narrower than in the West) is if government controls wages and curtails world trade. As John Meynard Keynes said, (paraphrasing) a government that insists on equality over freedom ends up with a society that has neither equality nor freedom. Japan is one of the most controlled industrialised societies.
In any case, Australia already taxes the more financially successful (at least when it comes to salary) more than the less so: we have progressive income tax. Of course the truly rich and savvy use trusts, etc to minimise that tax. So all you do is end up taxing the middle class more and more.
Alex