Why does Australia have low income concentration?

[buritobr]

In 1980, the top 1% of Australia earned 4.6% of the national income. This is skandinavian level. The income concentration increased in the last four decades, and now, the top 1% of Australia earns 9.1% of the national income. However, this is lower than it is in other English language countries.
Why is inequality in Australia low if we compare to other countries?

http://wid.world/share/#0/countriestimeseries/sptinc_p99p100_z/US;GB;AU;CA;SE/last/eu/k/p/yearly/s/false/2.8705/30/curve/false