In an attempt to get past the issues regarding small sample sizes, I went and did a somewhat larger sampling of 100 articles. I skipped disambiguation pages. I separately counted number of links in any "external links" section, number of links and/or paper references listed in any "references" section, and any links or citations within the body of the article itself. I didn't actually examine the contents of the references.
Of the hundred articles, 40 had no links or references of any kind.
18 had only a single external link. In most of these cases the single external link was to some form of "official homepage" which might or might not survive scrutiny by a WP:RS fundamentalist as "self-published" information.
If you discount the "external links" section as references then the number of completely unreferenced articles jumps to 71. I didn't actually example the contents of the external links sections to see whether they were usable as references or if they were just the first couple of Google hits, I can imagine a wide range of opinion here.
2 articles had only a non-specific "parts of this article were from the 1911 Encyclopedia Britannica" reference.
20 articles had inline citations.
So, from this one could say that somewhere in the vicinity of 40% are completely unsourced, at minimum.
==Raw data==
These are the articles I visited in my random walk and the reference counts I made at each, if anyone wants to double-check me or do any more advanced statistical fiddling (you may want to redo the "total" column since that was done by hand and not double-checked)
total, external links, non-inline references, inline citations, URL 0 0 0 0 http://en.wikipedia.org/wiki/1945_in_football_%28soccer%29 0 0 0 0 http://en.wikipedia.org/wiki/1959_in_Zimbabwe 0 0 0 0 http://en.wikipedia.org/wiki/1988_Grand_Prix_motorcycle_racing_season 0 0 0 0 http://en.wikipedia.org/wiki/Angel_%28Lilo_%26_Stitch%29 0 0 0 0 http://en.wikipedia.org/wiki/Biathlon_at_the_1960_Winter_Olympics 0 0 0 0 http://en.wikipedia.org/wiki/Bob_Bradley_%28composer/producer%29 0 0 0 0 http://en.wikipedia.org/wiki/Cardinal_sign 0 0 0 0 http://en.wikipedia.org/wiki/Carl_Henry_%28basketball%29 0 0 0 0 http://en.wikipedia.org/wiki/Chage_and_Aska 0 0 0 0 http://en.wikipedia.org/wiki/Challenging_Times 0 0 0 0 http://en.wikipedia.org/wiki/David_Jamieson_%28Canadian_politician%29 0 0 0 0 http://en.wikipedia.org/wiki/Fred_Binney 0 0 0 0 http://en.wikipedia.org/wiki/Gilbert_Kennedy%2C_4th_Earl_of_Cassilis 0 0 0 0 http://en.wikipedia.org/wiki/Glaze_%28painting_technique%29 0 0 0 0 http://en.wikipedia.org/wiki/Holland_III 0 0 0 0 http://en.wikipedia.org/wiki/Jebel_Dair 0 0 0 0 http://en.wikipedia.org/wiki/Lance_Hill 0 0 0 0 http://en.wikipedia.org/wiki/Legion_Sports_Complex 0 0 0 0 http://en.wikipedia.org/wiki/Life_In_The_So-Called_Space_Age 0 0 0 0 http://en.wikipedia.org/wiki/List_of_Ambassadors_from_the_United_Kingdom_to_... 0 0 0 0 http://en.wikipedia.org/wiki/List_of_mineralogists 0 0 0 0 http://en.wikipedia.org/wiki/List_of_places_in_Caerphilly_county_borough 0 0 0 0 http://en.wikipedia.org/wiki/Lower_New_York_Bay 0 0 0 0 http://en.wikipedia.org/wiki/Magic_circle 0 0 0 0 http://en.wikipedia.org/wiki/Marek_Zi%C3%B3%C5%82kowski 0 0 0 0 http://en.wikipedia.org/wiki/Mount_Brydges_Bulldogs 0 0 0 0 http://en.wikipedia.org/wiki/Murder_and_Killing_in_Hell 0 0 0 0 http://en.wikipedia.org/wiki/Non_sequitur_%28absurdism%29 0 0 0 0 http://en.wikipedia.org/wiki/Quebec_route_323 0 0 0 0 http://en.wikipedia.org/wiki/Rhizospalax 0 0 0 0 http://en.wikipedia.org/wiki/Rhythmic_Adult_Contemporary 0 0 0 0 http://en.wikipedia.org/wiki/Sar%C4%B1yah%C5%9Fi 0 0 0 0 http://en.wikipedia.org/wiki/Tequisquiapan 0 0 0 0 http://en.wikipedia.org/wiki/Tibor_Sekelj 0 0 0 0 http://en.wikipedia.org/wiki/Tulk_v._Moxhay 0 0 0 0 http://en.wikipedia.org/wiki/Way_Moby_Polka 0 0 0 0 http://en.wikipedia.org/wiki/William_Akin 0 0 0 0 http://en.wikipedia.org/wiki/William_Brandon_%28author%29 0 0 0 0 http://en.wikipedia.org/wiki/Woss%2C_British_Columbia 0 0 0 0 http://en.wikipedia.org/wiki/Xenia_%28automobile%29 1 0 0 1 http://en.wikipedia.org/wiki/College_Area%2C_San_Diego%2C_California 1 0 0 1 http://en.wikipedia.org/wiki/Achefer 1 0 0 1 http://en.wikipedia.org/wiki/Jason_Taylor_%28rugby_league_footballer%29 1 0 1 0 http://en.wikipedia.org/wiki/Charles_Canning%2C_1st_Earl_Canning 1 0 1 0 http://en.wikipedia.org/wiki/State_trials 1 1 0 0 http://en.wikipedia.org/wiki/Altenburg_Abbey 1 1 0 0 http://en.wikipedia.org/wiki/Carol_Drinkwater 1 1 0 0 http://en.wikipedia.org/wiki/Congress_of_Ukrainian_Nationalists 1 1 0 0 http://en.wikipedia.org/wiki/Daniel_Abugatt%C3%A1s 1 1 0 0 http://en.wikipedia.org/wiki/E-enablement 1 1 0 0 http://en.wikipedia.org/wiki/Helix_DNA_Client 1 1 0 0 http://en.wikipedia.org/wiki/HMCS_St._John%27s_%28FFH_340%29 1 1 0 0 http://en.wikipedia.org/wiki/London_International_Mime_Festival 1 1 0 0 http://en.wikipedia.org/wiki/Mishima%2C_Niigata 1 1 0 0 http://en.wikipedia.org/wiki/Morgan_Stanley_Capital_International 1 1 0 0 http://en.wikipedia.org/wiki/Nagakute%2C_Aichi 1 1 0 0 http://en.wikipedia.org/wiki/Parallels_%28TNG_episode%29 1 1 0 0 http://en.wikipedia.org/wiki/Pezinok 1 1 0 0 http://en.wikipedia.org/wiki/Polyus_Gold 1 1 0 0 http://en.wikipedia.org/wiki/Pulihora 1 1 0 0 http://en.wikipedia.org/wiki/Sentencing_Project 1 1 0 0 http://en.wikipedia.org/wiki/Sutherland%27s_Law 1 1 0 0 http://en.wikipedia.org/wiki/Til-Til 2 0 0 2 http://en.wikipedia.org/wiki/Michael_Avon 2 0 0 2 http://en.wikipedia.org/wiki/The_Trial_of_St._Orange 2 0 2 0 http://en.wikipedia.org/wiki/John_F._Forward%2C_Sr. 2 0 2 0 http://en.wikipedia.org/wiki/Pyramodon_ventralis 2 1 0 1 http://en.wikipedia.org/wiki/Energy_and_Environmental_Research_Center 2 1 0 1 http://en.wikipedia.org/wiki/Hedyeh_Tehrani 2 1 1 0 http://en.wikipedia.org/wiki/Gennadiy_Aygi 2 2 0 0 http://en.wikipedia.org/wiki/Arizona_Trail 2 2 0 0 http://en.wikipedia.org/wiki/Gilf_Kebir 2 2 0 0 http://en.wikipedia.org/wiki/Normanton_railway_station 2 2 0 0 http://en.wikipedia.org/wiki/Seven_Sisters_%28Moscow%29 2 2 0 0 http://en.wikipedia.org/wiki/The_Apprentice_3_%28Episode_8%29 2 2 0 0 http://en.wikipedia.org/wiki/Worlingham 2 2 0 0 http://en.wikipedia.org/wiki/Yvonne_Arnaud 3 1 0 2 http://en.wikipedia.org/wiki/Bessie_%28lake_monster%29 3 1 0 2 http://en.wikipedia.org/wiki/Biffa_plc 3 2 0 1 http://en.wikipedia.org/wiki/Too_Wild_Too_Long 3 3 0 0 http://en.wikipedia.org/wiki/Pontiac_Sunbird 3 3 0 0 http://en.wikipedia.org/wiki/Villa_Jovis 4 0 0 4 http://en.wikipedia.org/wiki/Dave_the_Barbarian 4 4 0 0 http://en.wikipedia.org/wiki/Regions_of_Denmark 5 0 0 5 http://en.wikipedia.org/wiki/The_Antidote_%28Moonspell_album%29 5 0 5 0 http://en.wikipedia.org/wiki/Anahit 5 0 5 0 http://en.wikipedia.org/wiki/Estuardo_Maldonado 5 2 2 1 http://en.wikipedia.org/wiki/Simone_Signoret 5 3 0 2 http://en.wikipedia.org/wiki/Angela_Watson 5 3 2 0 http://en.wikipedia.org/wiki/Francis_Benali 5 5 0 0 http://en.wikipedia.org/wiki/Deer_Run%2C_West_Virginia 5 5 0 0 http://en.wikipedia.org/wiki/Sumkidz 6 5 0 1 http://en.wikipedia.org/wiki/Word_of_Life_Church 7 3 4 0 http://en.wikipedia.org/wiki/Deolali 7 4 0 3 http://en.wikipedia.org/wiki/St._Regis_Mohawk_Reservation%2C_New_York 8 4 0 4 http://en.wikipedia.org/wiki/Mariska_Hargitay 8 8 0 0 http://en.wikipedia.org/wiki/Ernest_Lawrence 9 5 0 4 http://en.wikipedia.org/wiki/Norman_Naimark 14 9 0 5 http://en.wikipedia.org/wiki/Almighty_Saints 23 7 1 15 http://en.wikipedia.org/wiki/SQLite