Simple, it takes two people to do the job of one person...
It's almost standard across the board of employment anything. The common blue and white collars are less capable by today's standards.
When I was a young buck, two of us processed $1k of work an hour. By today's standards it take 10 people to do that exact same work. And...wait the price has increased easily by double or over. So by measuring it accordingly it would mean that two of us did the work of 20 people by today's standard.
Society is down the gutters and digging deeper...