Source: Phrasee [download page]
Notes: Data quality, segment selection and subject line are the elements that have the largest effect on email campaign response rates, according to a survey of 304 brand- and agency-side email marketers, predominantly from the US and UK. On average, while brand respondents perceive subject lines to have the largest effect, agency respondents placed data quality and segment selection first. Agencies also appear to place slightly more importance than in-house marketers on deliverability infrastructure and list size.
Other results from the survey indicate that when testing out subject lines, respondents most commonly test different call to action phrases (77%) and the length of the subject line (58%).
About the Data: The survey was fielded in October 2015 and had 304 respondents. 55% of the respondents were brand-side and 45% were agency-side, from across the world (approximately 60% US; 25% UK; 15% other).