After each mass shooting, gun control activists, bereaved parents and lawmakers reissue a call for more restrictive gun control laws. However, eight years after the shooting at Virginia Tech University that killed 32 and two years after the massacre at Sandy Hook Elementary that left 27 dead, Congress has not enacted substantial legislative changes.

The latest mass shooting in Oregon on Thursday again raises the issue of gun control and why efforts to pass gun law reforms have failed.

A simple reason is, perhaps, money. In 2015, the gun rights lobby outspent the gun control lobby about 6 to 1.

Data shows that the gun rights lobby, which includes groups like the National Rife Association and Gun Owners of America, consistently spends significantly more money in lobbying and campaign contributions than gun control groups like Everytown for Gun Safety.

The Center for Responsive Politics said that in the 2008 election cycle, gun rights organizations spent 34 times more on lobbying in 2008 than gun control groups. In raw numbers, that's $3.9 million versus $115,000.

While that money doesn't directly go to politicians, the money does go to lobbyists with access and who lawmakers often depend on for expert opinions and information.

Thursday's shooting at the Oregon community college is the 45th mass shooting this year, if defined as an event at which four or more people were killed. If defined as an event at which four or more people were shot, it's the 294th.