The dollar was defined as a certain amount of gold. That meant that gold was $20 an ounce. It was a controlled price. That is why the price of gold did not change so you cannot use that to claim that price inflation did not occur.
http://en.wikipedia.org/wiki/Gold
Perhaps you could explain for me what occured in the 1920's and 1930's.
Average hours worked in a week is not a very good measure of productivity or the value of your currency. You are right that if productivity increases that you can get the same output in fewer work hours. If you are happy with the same level of consumption, you may be happy to work fewer hours too. But people like to have more things. Today we have bigger houses than they did 100 years ago. They didn't have computers, cell phones, televisions (few even had radios 100 years ago), indoor plumbing, electricity, automobiles. People work more and want more money because they want more stuff. Laor unions came along and established the 40 hour work week. Before that, you had little say if your boss wanted you to work ten hours a day.
If you really want a better measure of purchasing power, do use hours- but instead look at how many hours somebody has to work to get something. Say a car or a house. Or an ounce of gold. You hint at this in your post:
Pick something and see how long you would have had to work to get it and compare that to how long you would have to work to get the same thing today. Since I have already mentioned that the price of gold was fixed back then, this would be a poor choice. Accoring to this, the average income was $750 a year in 1910
http://kclibrary.lonestar.edu/decade10.html It is not easy for me to determine what an average work week was on your graph so I am using this source
http://eh.net/encyclopedia/article/whaples.work.hours.us which says an average manufacturing worker put in about 55 hours a week. Since that says average week, I am assuming that it includes any time off during the year say for vacations if they got any. That comes out to 2,860 hours a week and at $750 a year an hourly wage of $0.26.
To keep things consistant, I will use a average work week for 1988 (the most recent one they list) of 42 hours a week for today (2100 hours a year). Seeking Alpha lists a current median income of $50,300 or $24 an hour.
http://seekingalpha.com/article/161271-u-s-median-income-from-1999-2009-no-gain-much-pain That is getting close to being 100 times more over 100 years.
OK- so we have our hourly wages. Now we need some prices. This is difficult since things change. People don't buy the same things they did 100 years ago.
Came across a few prices to compare here
http://www.foodtimeline.org/foodfaq5.html
Kellogs Cornflakes- just says "large size". 1910- 10 cents. If you had to work the same amout of time to buy that box today, it would be almost $10. So in terms of cornflakes, we are better off. Hershey Bar 9/16 ounce for 2 cents. I think the basic bar today is closer to two ounces- that would be about 3.5 times more or 7 cents. If we had to work the same amount of time today to buy that bar we would be paying about 7 dollars. Just a couple examples (pick anything you want to compare yourself). Are we working more hours because it takes us more time to buy the same things we used to? No. We are working more hours to buy more stuff.
Would you be willing to go from working 40 hours a week to 30 hours a week to help with the unemployment situation? This would be at the same hourly pay you currently receive. It would really help the economy out.
By the way, that eh.net.encyclopedia article has some great information about how come hours worked declined over time. As one would expect, there were many factors at work. The link again:
http://eh.net/encyclopedia/article/whaples.work.hours.us