Well I don't have time right now to look up any percentage changes that Google announced during major rollouts over the past couple of years, but I'm pretty sure that some of them were considerably larger than 1%. Besides, I don't think anyone ever figured out how Google measured those percentages, especially since the effects often seems far larger to non-Google observers. In fact many were large enough that people here on this forum noticed them and reported them before Google announced them. Google itself said some of them were major innovations to the algorithm, gave them special names, and bragged about how much the SERPs were improved.
There's a lot more to this that could be said, but I just don't have time right now, so will try to get back to it tomorrow.