This is just an observation I've made (and it may or may not be accurate)..
It seems like the Australian market (ASX) seems to open with large gaps more often than most other markets, namely the US (nasdaq, nyse etc) which, along with the higher commissions charged by Aus brokers, seems to make profitable day trading a bit harder on the ASX. Obviously it can still be done, and gaps sometimes reverse and close, but when they don't, the a large proportion of the daily movement happens after hours without the ability to day trade them.
Is this the case in your opinion? If so, is it because the Aus markets are more fundamentally affected by overseas news than, for example, the American market is affected by us?