I have added another new measure for sourcing levels, showing the percentage of "tallied" profiles (profiles from ThePeerage.com, Wikipedia and from our watchlists) at each sourcing level. Hopefully, over time, you should see the percentage of profiles at level 0 (unsourced) and level 0.5 (no primary sources) go down, and the number of profiles at level 3 (three or more primary sources) go up.
And still another new measure. This one shows the percentage of "tallied" profiles (profiles from ThePeerage.com, Wikipedia, and our watchlists) and WikiTree as a whole which are unsourced, partially sourced (at least a secondary source), and "fully" sourced* (at least three primary sources). This chart shows the difficulty in measuring sourcing levels for WikiTree as a whole, or even a single Last Name At Birth on WikiTree: for the tallied profiles, I depend on the counts in my spreadsheet, where I assign sourcing levels as I check the profiles. For WikiTree as a whole, I depend on WikiTree to get a count of profiles with the {{Unsourced}} template, and WikiTree+ (thank you, Aleš!) to get a count of profiles with either [[Category:More_Records_Needed]] or [[Category:Profiles_with_Incomplete_Sourcing]]. (I imagine that the Categorization Project will merge those two category hierarchies eventually.) But because both templates and categories are applied manually, there are a ton of profiles to which they should be applied, but haven't been yet. So that's why the tallied profiles show as less than 25% "fully sourced", while all profiles show as more than 95% "fully sourced". (This is one big reason why I keep saying that such-and-such a percentage of profiles on WikiTree is "supposedly" sourced.) Note that the average percentage of profiles with no primary sources across the 31 surnames that I'm tracking is about 5%, so the percentage for McDonalds is improbably low. (In fact, despite me adding the {{Unsourced}} template to dozens of McDonald profiles last month, the count only went up by three profiles. That might mean that somebody was following after me and sourcing profiles that I couldn't -- which would be great -- or it might mean that people are removing the {{Unsourced}} template from profiles that they manage because they're afraid it makes them look bad -- which would definitely not be great.)
* Yes, I know that three primary sources doesn't actually qualify as fully sourced, because ideally every fact stated in a biography should be backed up by at least one primary source, but I based my sourcing levels on the work of Paul Gierszewski, who first came up with a system for measuring how well profiles are sourced.