When you buy something it starts to depreciate. A car will be less reliable next year than it is now. If one of our customers installs a new cable this year, it will be less reliable next year, and even less reliable the following year. We all recognize this phenomenon as the aging process. The black line in the graph below is the post-installation failure rate for new cables installed at a U.S. Southwestern utility between 1969 and 2005.* In general, and as expected, failures increase as the years since installation increase.