Controlling risk in options trading
Could the differentiated coverage found in the study be attributed to the age factor-that is, could it be possible that the better coverage of U. sites was the result of those sites being on the Web for a longer period of time and thus having more chance of being discovered by search engines. We considered the possibility of examining this factor but decided that there was no reliable way to investigate this question empirically.
This bias renders the Internet Archive data inappropriate for our study. Although no reliable conclusion can be drawn on the age factor, we conjecture that the differentiated coverage cannot be totally attributed to website age.