Are people's political views changing this much over their lifetimes?

There is a very interesting post at OKCupid.com about how people's views supposedly change over their lifetimes. There might indeed be something to this, but I would have to see the data broken down differently before I believe it. We know that people raised in different eras have different political views. People who came of age during the 1980s tend to be more conservative than those who did so during the 1960s. The data in the above diagram is from a purely cross-sectional survey. What you really need to do is follow people over time, obviously a long period of time if you want a graph like the above one. For example, are people in their 60s more economically liberal because of their age or because they came of age in the 1960s or is it both? I suspect it is both, though I don't know how important the different factors are. If it is both, the figure above will tend to exaggerate the changes over time in a person's views.