"A pan-European epidemiological study reveals honey bee colony survival depends on beekeeper education and disease control"
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0172591

looking at the BIP  last 5 years 
Only about 4% of the "back yard"  (50 and under club) ran alcohol washes, those that didn't took 40% higher losses 
the backyard keepers that ran Amitraz  had only  25.4% losses 

As such I would not rule out experience/education, there seems to be a strong trend the better you take care of your bees the better the survival.
   
There is a trend in the hobby market to try to paint commercials as abusive to thier stock... the loss  % say other wise    

             ***********************************************
The BEE-L mailing list is powered by L-Soft's renowned
LISTSERV(R) list management software.  For more information, go to:
http://www.lsoft.com/LISTSERV-powered.html