"What happens –- now this is for a typical person; it doesn't happen for everyone, but on average -- ... is the person gets their first job (and) their salary is very low. If they do well and gain experience, what you see typically happen is their salary rises very rapidly for the first 10 years," says Dr. Walden, a professor of agricultural and resource economics.

"The next 15 years, their salary also rises, but less rapidly as they gain experience but perhaps at a slower rate," he adds. "And their salary in terms of inflation adjusted dollars peaks at about year 25. So year 25 would be when you are earning the highest (again in terms of constant purchasing power dollars).

"Then as you move toward retirement -– and let's say you are going to retire at 30 years –- your salary, again in inflation adjusted terms, actually goes down," he says. "The reason being that, hey, as you see retirement in your near future, your motivation slips, your productivity wanes -- and that's reflected in lower salary.

"So what this means," Walden concludes, "is that most people should see their best earnings on the job somewhere in their mid-50s."