One
Year with Harper Lee’s To Kill a Mockingbird and Go Set a Watchman,
Part 1
As
most people must have heard by now, Harper Lee died last week (Feb
19, 2016). I won’t go into her biography – after all, plenty of
people have done that already. Instead, I will present some
statistics on her Amazon book sales over the past year or so, as I
happened to have been following those intently over that time span.
My original motivation was to see how the original announcement and
subsequent publishing of “Go Set a Watchman” affected her sales
and reviews on Amazon. I had stopped my data gathering a couple of
weeks ago, but her death caused me to reconsider. Though it might
seem morbid, I was curious how her death affected her sales.
1
– Sales Rank and Key Events over the Year
The
graph below shows how sales of To Kill a Mockingbird (TKAM) and Go
Set a Watchman (GSAW) did over the timespan from early February 2015
to late February 2016, a period of a little over a year. The graph
is fairly self-explanatory, but since it may be difficult to read on
some screens, I will follow up with a narrative analysis.
Also,
keep in mind, that on this graph, when the lines go down, sales are
increasing. That can be a little confusing, rather like following
golf scores at the U.S. Open – lower numbers are better.
The
first key event was the announcement that a new book by Harper Lee
was in the works, in early February 2015. That kicked off my data
analysis, so I don’t have data preceding that event. As you can
see, that announcement led to TKAM being ranked at or near the number
1 spot on Amazon in early February 2015. As the later trend
indicates, TKAM’s baseline ranking was probably in the 500 to 1000
range, so this announcement had a huge effect on the sales for TKAM.
The book stayed in the top 100 for about a month, and within the top
500 right until the summer.
The
next key event was the pre-release of GSAW in late May 2015, followed
by publication in early July 2015. GSAW began at about rank 500 when
the pre-release became available (that means people could pre-order
on Amazon, and have the book sent to their Kindle or their mailbox as
soon as it was out). It then went steadily up in the ranks (down on
the graph), hitting number 1 early in July. TKAM pretty much
followed the same path, though it didn’t hit number 1 (its best
ranking in that period was number 5).
Both
books then lost those excellent rankings, drifting upwards to about
the 400 to 600 range over the next few months, until early December.
It should be noted, though, that GSAW’s sales ranks were better
than TKAM during that time.
The
next major event happened in early December, when GSAW won its
category in the Goodreads Book of the Year (2015) rankings. That had
GSAW back at rank number 1 in early December, though it drifted back
up into the 500 to 1000 range by early February 2016. TKAM got a bit
of a boost at this time from the success of its “sister book”,
but the effect was quite small, as the graph indicates.
The
larger markers on the graph show Christmas. As you can see, TKAM got
a bit of a Christmas boost, dropping a couple hundred places in sales
rank, from about 800 to about 600. The Christmas sales rank boost
for GSAW was very modest, more of a Christmas blip, really.
Then,
of course, we come to Ms. Lee’s death last week. As I noted in the
intro to the blog, I had stopped gathering data in early February
2016, thinking that one year was plenty. Thus, the interruption in
the time series in the two weeks before her death.
But
the important finding is obvious – death can be a good career move,
at least for a while. Both books are back to the top 100, with TKAM
in the top 25 over the past 3 days (Feb 20 to 22) and GSAW in the 50
to 100 range. Time will tell how long that effect lasts – based on
previous key events, one would expect both books to be in the 500 to
1000 rank range within two or three months.
2 – Sales and Key Events over the
Year
The
next graph is a bit more speculative. I used Hugh Howie and Data
Guy’s sales rank to sales conversion formula. This is a power law
mapping, based on crowd sourced author data indicating how their
daily sales and sales rank correlate. The exact form of the “real”
underlying function is unknown, so I am using Data Guy’s version of
this as a “best guess”.
|
Sales
Rank
|
Sales
Per Day
|
|
1
|
7,000
|
|
5
|
4,000
|
|
20
|
3,000
|
|
35
|
2,000
|
|
100
|
1,000
|
|
200
|
500
|
|
350
|
250
|
|
500
|
175
|
|
750
|
120
|
|
1,500
|
100
|
|
3,000
|
70
|
|
5,500
|
25
|
|
10,000
|
15
|
|
50,000
|
5
|
|
100,000
|
1
|
|
100,001
|
-
|
Using
the Data Guy mapping, and converting to a continuous function gives
(approximately):
Sales
= 10 (-.77*Rank+4.30)
I
should note that the continuous function estimates somewhat high at
the very top ranks, compared to the mapping above. But it is not
unusual for there to be uncertainty in real world applications of
power laws in the extreme ends of the range.
The
key events and the responses to them are the same as in the previous
graph, though the scale of the effects are very different. That’s
because of the power law nature of the relationship between sales
rank and sales. The number of sales associated with a low ranking is
amplified by the power law, compared to the number of sales
associated with a higher ranking.
For
example, we see that the Goodreads Award boost for GSAW is not nearly
as prominent in this graph, as it was in the ranking graph. That’s
because the award only resulted in the book going as high as 4th
rank, and the boost to better than 100th
rank only lasted for about a week. Similarly with the sales boost
caused by Ms. Lee’s death.
The
third graph, below, shows the same data as the previous graph, but
uses a logarithmic scale for the y-axis, sales. That allows one to
see the small scale effects better, that are obscured by the scale
differences in the original graph. It also makes clear that neither
books sales ever dropped below 100 copies per day.
The
final graph is similar to the second graph, but smooths the data with
a 7 day moving average filter.
In another blog,
I will analyse the trend in Amazon reviews over this time period, and
make some observations about the interaction of sales rank and
numbers of reviews.
Finally, of course, I have to include
the traditional “call to action” – i.e. remind you that you can
buy one of our books. Since Harper Lee wrote about the social and
racial complexities of the American experience, I will offer up “On
the Road with Bronco Billy”, a travelogue and cultural study of
late 20thcentury America, as seen from the cab of a big rig. It also includes
some observations on race and class in America, though not with so
fine a literary touch as Harper Lee’s books.:)
On the Road with Bronco Billy - A
Trucking Journal
Kindle Edition
What
follows is an account of a ten day journey through western North
America during a working trip, delivering lumber from Edmonton
Alberta to Dallas Texas, and returning with oilfield equipment. The
writer had the opportunity to accompany a friend who is a
professional truck driver, which he eagerly accepted. He works as a
statistician for the University of Alberta, and is therefore is
generally confined to desk, chair, and computer. The chance to see
the world from the cab of a truck, and be immersed in the truck
driving culture was intriguing. In early May 1997 they hit the road.
Some time has passed since this journal was written and many
things have changed since the late 1990’s. That renders the journey
as not just a geographical one, but also a historical account, which
I think only increases its interest.
We were fortunate to
have an eventful trip - a mechanical breakdown, a near miss from a
tornado, and a large-scale flood were among these events. But even
without these turns of fate, the drama of the landscape, the close-up
view of the trucking lifestyle, and the opportunity to observe the
cultural habits of a wide swath of western North America would have
been sufficient to fill up an interesting journal.
The
travelogue is about 20,000 words, about 60 to 90 minutes of reading,
at typical reading speeds.
