Subject lines: Amazon's lessons on length

I once interviewed a CEO who described his online retail philosophy as WAD-based. Whatever Amazon Does.

So what might WAD teach us about email subject lines?

Here's Part 1 of an analysis of the last 187 promotional emails I received from Amazon.com, Amazon.co.uk and Amazon.de.

Length

For the stat fans, the average subject line length used by Amazon was 57 characters.

But before we all carve that number in stone as something to aim for, consider the graph below. It charts the number of times a particular length of subject occurred in those 187 emails:



Blimey.

While the average is 57 characters, most subjects are actually shorter than that: between 39 and 52 characters. And there are still plenty of examples that are much longer than that average. In fact, the longest comes in at 140 characters! (The shortest is just 19).

So what's going on?

Many marketers assume that shorter is better for subject lines. That's not entirely true. The best subject line length is one that uses as few words as possible to provide the information or incentive that gets the reader to open it.

That's a little more nuanced than simply striving for 50 characters or less.

So, yes, keep it short. But not at the expense of important words that can contribute significantly to higher responses. (For more detailed discussion of this, see Part 1 of last year's subject line series and the scrabble theory post.)

Amazon is taking this approach, adjusting the length of the subject line to need. A simple email with offers on TV boxed sets looks like this:

TV DVDs from £4.97 at Amazon.co.uk (34 characters)

It's short and snappy.

But a specific book recommendation is longer, ensuring that the words likely to trigger my interest (the book's title and/or author) are included:

Save 22% at Amazon.com on "Speak: 10th Anniversary Edition" by Laurie Halse Anderson (84 characters)

Those specific product offers are based on my previous purchases or where I spent time on the various Amazon websites. So they're highly targeted in theory (a topic for another day).

The problem with such lengthy subjects, though, is that a lot of them get truncated by the various email systems out there. My Windows Live Hotmail interface, for example, only displays 29 characters the way I have it setup.

Which is why the very important words need to be at the start.

Consider:

Jetzt neu: "Fantastic Beasts and Where to Find Them: Comic Relief Edition" von Joanne K. Rowling

The new book announcement (which is what "jetzt neu" implies in German) is fine in theory. I've bought enough Harry Potter books through Amazon Germany, so I'm likely interested in anything new from J.K.Rowling. Super targeting!

Here's how it looks in my Thunderbird inbox:



The targeting value is lost in this example, because the hottest "trigger" words are actually the author's name. Which does not appear.

You might think it's a simple matter of reversing the sequence of data pulled from the database: author - title, rather than title - author.

The problem is that the relative importance of a product's name, function and brand is not always the same.

In the above example, the author's name was critical. So reversing the order would work well. But in this next example, it's the title that's critical. The product is a sequel to the bestselling Gruffalo book:

Jetzt neu: "Gruffalo's Child (Gruffalos Child Big Book)" von Julia Donaldson

In this case, a truncated subject line is no problem as the key information is still visible.



Reversing the order to author - title would hurt the targeting (with all due respect to Julia Donaldson).

There is no simple answer to the problem since it relates to automation and product database fields, for which I have less expertise than my cat.

Perhaps those looking to integrate email with customer purchases and browsing behavior can have a single product field in their database specifically for use in email subject lines.

So our first example might look like this in an email:

Jetzt neu: J.K.Rowling's "Fantastic Beasts and Where to Find Them: Comic Relief Edition"

And the second like this:

Jetzt neu: "Gruffalo's Child (Big Book)" von Julia Donaldson

Perhaps some retail email experts out there can offer more advice on dealing with this issue.

Amazon's longest subject line illustrates another problem with automated emails pulling data from a product database:

Save 25% on "A Cook's Book of Sauces: Mayonnaise Hollandaise Bearnaise: Mayonnaise, Hollandaise, Bearnaise (Murdoch Books)" by Murdoch Books

You can see a similar problem with word repetition here:

Save 26% on "Biker Mice From Mars - New Cats In Town [DVD]" on DVD

So when people talk about triggered emails etc., be aware that it's not a perfect technology!

OK, next week we'll look at some more Amazon-inspired subject line insights on personalization, branding etc.

More on subject lines | Tags: email marketing, subject lines

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