This is because of how Tableau interpretes the "Week #".
Here is a KB on the subject: http://kb.tableau.com/articles/issue/getting-complete-week-data-across-two-years
(I think there is also an idea floating around about this as well)
Hope this helps!
Thanks for replying. I see what you're saying and I checked out the KB, but this time it isn't a Tableau interpretation. The data that we aggregate and feed into Tableau has the weeks classified as 1-53 already. So I'm trying to figure out how to manipulate that in Tableau. I tried your formula, which seemed to work on the surface, but now I'm only getting Week 1 data for just 2015. Then, my 2016 Week 1 data populates under Week 2. So now, I just want to pull the data I have for 2016 back one week. Hope that makes sense. I've attached the screenshot.
Week 53 2015 #2.JPG 33.0 KB
Ah, I understand now.
How about a calculated field that does the weeknumber -1 when the year has this issue?
If [Year] = 2016 THEN [WeekNum] - 1 ELSE [Year] END
Actually, looking at your screenshot: if you updated the weeknumber - I think the year might be your issue. Do you have twice the normal amount of data in week 1 - 2015?