Heteroscedasticities

Sunday, September 07, 2008

How green was my valley

A friend of mine, very world-weary at twenty-seven, today commented how degraded the art of the modern world is. By art, he seemed to mean all creative endeavour, including television. Why, he said, look at the sitcoms of the early years of our lives. What today can compare to M*A*S*H? We reluctantly watch Family Guy because everything else on TV is worse. The best-rated programmes are reality shows. What does it say for us that we are headed so rapidly downhill?

When I was young, I would look at houses around me that were more than a hundred years old, and was always struck by how beautiful and functional they were, how solid and well-built. At twelve, I developed the idea that the root of all trouble lay in the invention of cement, and that mud as a building material would have served us well until the end of time.

The common thread here is that the only old shows that we have seen are the good ones, and the only old houses that have survived for me to marvel at them are the well-built, beautiful and functional ones. This is what finance academics call survivorship bias.[1]We see only the good/strong/successful members of a population, and we conclude that every element of that population was just like that.

But of course they weren't. There were bad TV shows in the eighties, just as many as there are now. None of those were kept on VHS and converted to DVD; none of them survive in our memories. Badly-built houses fell down; ugly houses were torn down by the thankfully more sensitive descendants of the original barbarians.

Homesickness seems to work on the same principle. It isn't as though you will be sadder where you are going than you were where you were(always providing, of course, that you aren't going to be a galley-slave somewhere, or worse, a grad student). You remember pleasant times, you don't remember sad times. I wonder why that is. Maybe it's an evolutionary mechanism to keep us from drowning in the depths of our own despair.

Of course, it may be peculiar to me that I remember happiness more than I remember sadness, in which case my elegant theory of homesickness will be severely tested.


Footnotes:


[1]The earliest applications were to mutual fund returns. If we have a ten-year database of mutual funds, but we only keep those mutual funds that survive all ten years, then we are implicitly throwing out all mutual funds that did badly (and hence failed), upwardly biasing any return measures we calculate on the remaining.

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