Does concealed carry save or cost lives

[mileslunn]

In US, every state in some form allows concealed carry with over 20 having constitutional carry.  Rest are mostly shall issue while may issue states very much a minority.  No jurisdiction in US outright bans concealed carry, but a few make it extremely difficult.  Outside US, most OECD countries either ban it outright or make it very difficult to get.  UK & Japan ban it outright while Canada, France, Germany & Italy make it very hard and only issue it in very limited circumstances.  In Canada, I believe the number of individuals with such permit is in the single digits out of 40 million. 

So what are your thoughts?  Does it help save lives as gun lobby claims?  Does it make society more dangerous? Or is it irrelevant and other issues matter more.  If no impact that can also mean depends on details as some have said if requires licencing, extensive background checks, and training it can be beneficial but if freely available to anyone who wants it more risky.  I am personally opposed to idea myself and probably fair to say where I live in Canada very few want it here.  But like to hear from others on this including Americans as know issue much more divisive there with public split on issue.