Purchasing power parity. You're conflating a drop in the factor of human labor with a drop in the vlaue of that labor, but they're not the same thing. For example it may take me only 1 hour to do in Excel what would take me 3 hours to do with pen and paper, but the value of an hour of my work has not dropped; it's probably risen due to the greater complexity of accounting tasks I can perform and my increased technical knowledge. I spend 3x less time on each client, but I can handle 3x more clients. My wafes ought to stay the same in real terms, or even rise depending on how well I can operate Excel. Your cost to get your books done may have fallen in real terms thanks to my doing it faster with Excel, but my hourly rate has not.

Under deflation, though, everyone has less money so I have to keep cutting my rate to stay competitive. Now even though I'm more productive I'm getting a lower return on my productivity. Arguably,this is a problem currently facing much of the labor force in the US.