If you visit the Language Spy political trend analysis tool on a regular basis, you'll be familiar with the list of popular searches. At the moment for example you'll find very topical searches related to military action in Syria and to David Cameron's continuing troubles over Europe. These searches change over time as you might expect, reflecting the interests of the site visitors and the political stories of the day.
You'll also notice a few unexpected searches. The candidates in summer 2015's Labour party leadership race for example, or the party leaders from the last general election. Stories from months ago, still making waves.
Of course, these are not on the minds of site visitors. These are "zombie searches", generated by links and Tweets generated when they were current, and still existing out there on the internet, appearing in search engine results, generating traffic.
It would be tempting to put in a blacklist, to exclude these searches by name. But on reflection it's worth leaving them, for they provide a surprising second view on which stories made the most waves. Of the hundreds of searches that do make it onto the list of popular searches they are the ones that persist, and that persistence is a measure of their importance. They do fade away - for example one relating to a sex scandal surrounding a now-dead former prime minister has now slipped off the list - so the speed of their roll-off can serve as a gauge of their importance on a longer scale than just that of the moment.