More than 40 million emails sent by Boomerang users were analysed to determine the optimal readability for maximising open and clickthrough rates.
Average rates of replies to emails written at different levels:
1. A kindergarten reading level: 46%
2. A 3rd grade reading level: 53%
3. High school reading level: 45%
4. A college reading level: 39%
Shorter words and simpler sentences are an easy method to achieve a third-grade reading level.
Source: www.fastcompany.com