Sydney unit prices rose by +4 per cent over the year to September 2016, according to Residex, to be be +20 per cent higher over the last two years.
Interest rates have fallen sharply since then too, so the supply response should now be in full swing.
Furthermore, there has been a recent uptick in house vacancy rates in Sydney to a year-high of 2 per cent, while unit vacancies tightened as tenants apparently look towards the slightly more affordable options.
I've linked a copy of the 40-minute presentation below if you're interested in watching it.
It's worth acknowledging that house prices have been rising faster than this in some the inner suburbs of Sydney, while median prices may on occasions understate price growth as affordability pressures bite (as properties in the lower price quartiles may transact more frequently).