It may also be a result of greater stiffness required for the captive pop-tab opener to work properly. There's an interesting Slate article[1] about the comple

It may also be a result of greater stiffness required for the captive pop-tab opener to work properly. There's an interesting Slate article[1] about the complexity of what appears to be a such a simple feature; in order to achieve the force necessary to rupture the can opening, the tab pivot transitions between a first and second class lever. There's a good video somewhere showing the principles, but I can't seem to find it. Returning to the 'pressure' argument, recall that most drinks cans have a domed bottom which provides comparatively greater strength than the flatter top. [1] http://www.slate.com/articles/life/design/2012/09/can_tabs_how_aluminum_pop_tabs_were_redesigned_to_make_drinking_soda_safer_and_the_world_a_cleaner_place_.single.html http://www.slate.com/articles/life/design/2012/09/can_tabs_h...