that a user’s past tweeting success was far more important. Even so,
their overall prediction ability was fairly limited. Despite having the
sort of dataset a disease researcher could only dream of, the team
could explain less than half the variability in cascade size.
So what explained to the other half? The researchers
acknowledged that there might be some additional, as-yet-unknown
features of success that could improve prediction ability. However, a
large amount of the variation in popularity will depend on
randomness. Even if we have detailed data about what is being
tweeted and who is tweeting it, the success of a single post will
inevitably depend a lot on luck. Again, this shows why it is important
to spark multiple cascades, rather than trying to find a single ‘perfect’
tweet.
Because it’s so difficult to predict a tweet’s popularity before it’s
been posted, an alternative is to wait and look at the start of the
cascade before making a prediction. This is known as the ‘peeking
method’, because we’re looking at data on the early spread before we
predict what will happen next.[56] When Justin Cheng and his
colleagues analysed sharing of photos on Facebook in 2014, they
found that their predictions got much better once they had some data
on the initial cascade dynamics. Large cascades tended to show
broadcast-like spread early on, picking up lots of attention quickly. Yet
the team found that some features were more elusive, even with a
peeking method. ‘Predicting cascade size is still much easier than
predicting cascade shape,’ they noted.[57]
It’s not just social media content that is easier to predict after some
time has passed. In 2018, Burcu Yucesoy and her colleagues at
Northeastern University analysed the popularity of books on the New
York Times bestseller list. Although it’s very hard to predict whether a
given book will take off in the first place, books that do become
popular tend to follow a consistent pattern afterwards. The team
found that most books on the bestseller list saw rapid initial growth in
sales, peaking within about ten weeks of publication, which then
declined to a very low level. On average, only 5 per cent of sales
occurred after the first year.[58]