With best practice guidelines for subject lines recommending marketers to keep subject lines as simple as possible, many emails are sent with subject lines with an understandability level aimed at people aged 9-14. However, as the stats show, the average open, click and click-to-open rates all tend to improve the more complex the language in the subject line. In fact, the subject lines that performed the best were those with the vocabulary of a 16-to-18-year-old. Get the full story at Econsultancy