I have been tracking several statistics that approximately represent the quality of the Wikitree database. The last update was posted in June 2018 in G2G. Following is a summary of current information:
Overall status: 18.8 M total profiles; 15.1 M or 80% are connected; 4.6 M or 25% have DNA links (from Wikitree info).
Profiles with known internal consistency issues: 133,000 or 0.7% of all profiles (based on Suggestions report data).
Sourcing: about 11% with 3 or more original sources, 32% with 1-2 sources, 13% poorly sourced, 29% unsourced, and 15% Unavailable (Unlisted/Red/Orange privacy) (based on random sampling).
Identified Duplicates: about 8,805 or 0.05% (based on Suggestions report data).
Compared with June 2018 when I last reported on these statistics, there are 1.3 M more profiles. Of particular note, the number of profiles with known consistency errors has dropped from 154,000 in June to 133,000 now. Also, the fraction of profiles with 1 or more sources has increased from 38% to 43%, an increase which may be more than just sampling uncertainty (+/-5%).
A Free Space page with graphs, historical data and technical details is available here:https://www.wikitree.com/wiki/Space:Wikitree_Statistics