How is Long Term Disability effecting Employment? or is it?

     I read this article from AEI about how SSDI is effecting the labor force participation rate. (You can find it here ).  Its a great article.  However they missed one thing that I think is important, that is as the work force declines (lower work force participation rate) and the number of people on SSDI increases it puts more and more pressure on production of those who are left working.  In other words those that are still working are forced to produce more and more.  This isn't a huge problem if technology keeps up with the rate of decrease in work force and the increase in disability.  If not those who are left working will have to produce more and more while getting less and less for their effort.  The last question is what will they do when it becomes to much?