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The first thing I think of is that you're measuring pageviews instead of sessions. If you put a lot of effort into streamlining the user experience, wouldn't you expect a decrease in pageviews as users are finding what they need faster? I would check a few different things to gain a more complete picture. First, check your sessions instead of pageviews. If sessions are trending the way you expect them to compared to the previous year, then maybe the redesign impacted user behavior so they're hitting less pages on the site. Next I'd see if there was any differentiation between mobile, tablet, and desktop pageviews that are skewing the data. Since the site is now responsive I wouldn't be surprised to see a difference in user behavior on mobile devices, and that may be impacting your pageviews. Lastly, why not segment and compare by traffic source? If you can identify a sharp drop from a particular source you might be able to gain some insight there. An easy method of viewing this is to create a collection of pie charts or bar graphs so anyone can quickly see where the change was. There are other ways you can slice and dice and segment your data to tell your story, but I would start there.