The rate of 50% has been thumb-sucked because they copied the Aussie mining tax policy word-for-word, and that policy has raised a pittance since its inception (zero AUD in its first quarter), and they therefore want to maximise what they get when the odd opportunity comes around to tax the mining houses.
What they fail to realise is that increasing the tax won't result in any more payments, as the companies will simply divert pre-tax profits into infrastructure projects. These projects don't need to be profitable. They are in fact better off not profitable, so they're simply encouraging that the industry as a whole becomes less competitive or waste cash. Take into account forex risk and lower export demand and you have a recipe for failure.
Australia has shown that this sort of tax is a ludicrous proposal and only serves to hamper investor confidence, not only in the sector but in the country as a whole. Investor confidence fell considerably after its approval.
While we punish our miners for success, the rest of Africa, particularly West and East Africa are trying to butter-up investors to mine in their country. While Billies and Tinto pull out of South Africa because of the higher costs of doing business here, the rest of the continent are doing what they can to poach them away from us. They're winning. Recently the IMF told Tanzania that they had to start taxing mining companies at a higher rate because they were trying to increase investment in this space and lowered the rate for mining houses.
In 7 years, 21 new gold mines began operating in West Africa. That is a staggering number. In the same period, we lost mines at a staggering rate and this year saw a pullout from Billies in all future projects. In other words, they are no longer investing in SA, effectively.
But go ahead, ANC. Tax, tax, tax away, you bunch of communist pricks. Eventually you will get your wish and will have control of the mines, but it will be so bloody expensive to mine them and demand for SA gold will be next to nothing - you'll be begging the rest of the world to come back and help! And they won't!