windshields as vehicle structure

It definitely depends on the particular vehicle, but my understanding is that most vehicles depend on the stiffness of the windshield in helping support the roof. I have heard numbers approaching 25% of the support strength along the forward part of the roof-line is due to the windshield, thus relieving some of the stress on the A-pillars. Curious on the origin of your question. Hope this helps.

Does anyone know how much windshields are regarded as strength for vehicle structure?