  Event-based collections are often started with a web search, but the search
results you find on Day 1 may not be the same as those you find on Day 7. In
this paper, we consider collections that originate from extracting URIs
(Uniform Resource Identifiers) from Search Engine Result Pages (SERPs).
Specifically, we seek to provide insight about the retrievability of URIs of
news stories found on Google, and to answer two main questions: first, can one
"refind" the same URI of a news story (for the same query) from Google after a
given time? Second, what is the probability of finding a story on Google over a
given period of time? To answer these questions, we issued seven queries to
Google every day for over seven months (2017-05-25 to 2018-01-12) and collected
links from the first five SERPs to generate seven collections for each query.
The queries represent public interest stories: "healthcare bill," "manchester
bombing," "london terrorism," "trump russia," "travel ban," "hurricane harvey,"
and "hurricane irma." We tracked each URI in all collections over time to
estimate the discoverability of URIs from the first five SERPs. Our results
showed that the daily average rate at which stories were replaced on the
default Google SERP ranged from 0.21 -0.54, and a weekly rate of 0.39 - 0.79,
suggesting the fast replacement of older stories by newer stories. The
probability of finding the same URI of a news story after one day from the
initial appearance on the SERP ranged from 0.34 - 0.44. After a week, the
probability of finding the same news stories diminishes rapidly to 0.01 - 0.11.
Our findings suggest that due to the difficulty in retrieving the URIs of news
stories from Google, collection building that originates from search engines
should begin as soon as possible in order to capture the first stages of
events, and should persist in order to capture the evolution of the events...
