There definitely are. I don't have any of those statistics on hand.
It goes without saying that when you get the opportunity to negotiate, you get good working conditions and you get better working conditions, and you have the leverage of the labour union in order to obtain those, especially with things like enforcement. The two things unions can do for workers are to negotiate contracts and to enforce those contracts. Throughout my work experience, and even in my personal life, for workers who face bad employers without the protection of a union, it's a lot more work to get those employers to follow the rules and treat workers with respect.
As I mentioned, it was actually much easier earlier in the century to form unions. A lot of provinces have put in place two-step laws for unionization, to allow employers to break down unionization drives. We're seeing now that some provinces—notably B.C.—have the card check law, which makes it a lot easier and fairer for workers to organize their workplaces.