How's your tweet timing?
Optimising your social sharing on Twitter can be a real science. I've posted about and followed Dan Zarrella's research for the last few years so his latest insights are well work digesting.
The first graphic is focused on USA timing so people down-under will need to mentally adjust the data.
You should also know where in the world your followers are from so you can accordingly time your posts to each timezone. I found a fantastic tool twocation.com, in less than 1 minute it will calculate what percentage of your followers are located in each country.
I also use an app called Fruji which is a powerful Twitter analytics tool. In the graphic below it's mapped out my Twitter activity and my followers responses to my activity for my location [Auckland]. This helps me refine and adjust my activity to coincide with when my followers are more likely to engage.