Source:SMH article
I don't have anything definite to add to the article, so what follows is really speculative. One thing that came to mind was that this graph roughly represents the state of the class struggle. By 1979, after Vietnam, the capitalist class were on the backfoot, but about to take the offensive internationally: Thatcher, Reagan and Gorbachev took power (none of them capitalists themselves per se, but all representing bourgeois interests) and the pendulum started to swing back. Although it's also true that the international and Aussie economies were in the doldrums at the same point and then recovered, which certainly indicates that economic growth doesn't trickle down all that much but rather hugely boosts income inequality. However, one wonders whether this economic recovery wasn't in part due to the regrowth of imperialism in the same period.
A tantalising comment in the SMH article is that is that the massive growth in executive incomes is skewing the whole picture of earnings. Which makes me wonder whether this enormous growth is not a major driver of the inflation which is resulting in the flagellation of the indebted masses.