The good people at leedsindexers.co.uk
Have found some major transcription discrepencies in a search they did on the 1901 census:
(online – http://www.1901census.nationalarchives.gov.uk/) for Yorkshire – comparing them with the actual census.
During the course of writing the GuessTimator software we have worked with the data on the PRO site. We obtained and checked the 1st person in every enumeration District in the Yorkshire area. We were shocked to find that approx 10% of these records were inaccurately recorded. No wonder people have problems finding ancestors.
– End Quote
No wonder indeed!