That's what the guys at Fractl have done by looking at more than 26,000 emails to see which words gave increases n open rates compared to others in a field or category.
A couple of clear things jumped off the page at them. First of all, as we all know people like to imagine and 'see' something as you paint a picture for them. Hence, visual words, such as "image" and "size" saw an uplift of around 20%. It's the same for geography. If you can tag in an email line where the person is, or to where your email refers, open rates go up. Out of interest, the term UK gets an uplift of 22%. The research attributes this to people liking that their emails have been personalised and summed around their geography.
In the age-old debate over word length, the researchers point out that the best performers in their study average out at around 10 words. Sounds about right, doesn't it? Like underwear, long enough to cover what needs to be covered, but short enough to be interesting!
The big surprise, hpwever, is the words that really do not perform at all well. They are summed up as the words that marketers think are truly dynamic but which are now so overused that consumers either filter the term out or feel t will require too much of their attention. Believe it or not -- video, data and interactive are among the five most over-used subject terms which actually underperform. The big takeaway the researcher offers is to never tell them how a consumer could discover something, and stick to what they're going to come away with.
So, subject lines about ten words with geo references and words that related to seeing something are the big hits. Telling people you're going to show them a video or interactive infographic are, perhaps surprisingly, the damp squibs of subject lines. Good to know.