There are wild swings on the Australian stock market today as half-year reporting season cracks open surprising and disappointing results.

Over the past five sessions: Breville Group has jumped 28 per cent, Altium 22.3 per cent, Domain Holdings, 21 per cent, and Aveo Group 18.4 per cent. On the downside, Bingo Industries is down 42.7 per cent, Emeco Holdings is down 25.5 per cent and Blakcmores is down 23.4 per cent.

Portfolio manager at Tribeca Investment Partners, Jun Bei Liu, says the size of the swings speaks to the light volume of trading but also investors over-reaction.

"The market has become skewed in terms of expectations," she says. "The minute a company disappoints, investors don't want to have any money in it. It is quite polarised at the moment."

The quantum of company downgrades or upgrades is also unusual, she says. For example Bingo Industries downgraded its earnings guidance by 20 per cent on Monday. And these large changes are taking analysts and the market by surprise.