Saying that the number of guns in private hands is higher today in Canada and Australia than it was 20 years ago doesn’t really say much. It could be one higher or a lot more. What is the basis for you saying that — have you a link to something? Is it a significant increase or one to be expected based on population growth?
What really matters is the effect of new gun laws on mass shootings and murders in Australia and there is no doubt about that. In the 18 years before the gun ban in Australia there were 13 fatal mass shootings in that country. In the (now 21) years since, there have been none.
A 2012 study by Leigh and Neill Australian National University and Wilfrid Laurier University (Canada) looked at the firearm ban and buyback in Australia. They determined (amongst many other things) that,
…there was a statistically significant decline in firearm deaths in states with higher firearm buyback rates.
Here’s a link to the study: