Like many things, there are a few ways to analyze incomes.
People on average, however, have continued to increase their standard of living e.g., larger houses, more or nicer cars, having more things/gadgets, etc. This is at least partially due changes in the credit/financing markets, especially longer available terms. 20 year mortgages used to be the norm, now it’s 30 years. 35 month financing on new cars used to be the norm, now it's about double that.
Unfortunately, instead of people taking advantage of longer term financing to bring down their monthly expenses, they use it to buy more, bigger or nicer stuff. If lifestyles today were as "modest" as they were 50 years ago, there would be much fewer personal money issues.