How much of that work was truly work? Quality work where we are suppose to be doing what we were paid to do instead of extraneous activities. I had to chuckle at this one as most of the details in the next infographic is probably true (unfortunately for employers). What causes slacking? Day dreaming, summer heat, or perhaps just a dire need of vacation?
Effects that cause workers to be tired and weary are legitimate excuses for slacking in my opinion. We are only human after all. I don't think most other reasons for being lazy are very valid but I'm not one to judge as I would also like to reserve my right to be spontaneously lazy =)