Shiller showed that irrational exuberance is a thing. Stock investors are not 100 percent rational, as the Buy-and-Holders posited. They get carried away. They push prices up to crazy levels and then we all pay the penalty when those prices inevitably come crashing back down to earth. It’s a big advance in our understanding of how stock investing works. It changes everything. If irrational exuberance is a thing, we need to adjust the number on our portfolio statement for the effect of the pretend money if we want to know the true amount of our accumulated life savings. If irrational exuberance…