Your chart is gun deaths per 100,000 but the other chart posted was total gun deaths in Australia, so that's not a fair comparison. Here's the gun deaths per 100,000 for Australia: http://www.gunpolicy.org/firearms/compareyears/10/rate_of_al.... You can see from the chart that both the US and Australia show a significant drop in the 1990s. The US levels off by 2000, but Australia keeps dropping through about 2005. It's entirely possible that the further drop could be due to Australia's 1996 gun law.
> It's entirely possible that the further drop could be due to Australia's 1996 gun law.
Since the trendline is basically the same until it tapers off around 2003, it's hard to say; but since the trend is identical (and identically noisy) before and after 1996, it is unlikely it had any effect. You would expect an increase in the trend if it did.
Especially when you compare this to the identical trend in the U.S.[0] and Canada[1] at the time, it's hard to make a case that any effect was experienced.
Homicide in western countries just sorta trended downward since the mid '80s until the early 0ughts.
When gun violence decreases, fatalities decrease. A violent attack without a gun is less like to result in fatalities. A suicide attempt without a gun is less likely to result in a fatality, and so on.
Nonsense... Proof: Any other country that has introduced strict gun control. It makes all the numbers go down.