And the data for the two decades before that should be tossed out because of the global housing crisis, the sovereign debt crisis, and all the reverberations from that.

And the data for the two decades before that obviously needs to be tossed out because of the one-off nature of the dot-com boom, the dot-com crash, 9/11, and so on.

And before that... point is, you don't get clean data in economics. There's always something big going on, there are no double-blind trials to run, etc. It's called the dismal science for a reason. But that doesn't make it useless.