well, "economically viable" doesn't necessarily mean scraping the bottom. For example the great pyramids of giza are very solidly built. You certainly don't ex

well, "economically viable" doesn't necessarily mean scraping the bottom. For example the great pyramids of giza are very solidly built. You certainly don't expect that level of build for every commercial or residential building out there. Now, on the other end of the spectrum you can have buildings that can collapse on minor earthquakes. There is a balance somewhere in the middle.