How increasing the relevancy of a subject line impacts email open rate Experiment ID: #8272

Hillsdale College

Founded in 1844, Hillsdale College is an independent liberal arts college with a student body of about 1,400. Hillsdale’s educational mission rests upon two principles: academic excellence and institutional independence. The College does not accept federal or state taxpayer subsidies for any of its operations.

Experiment Summary

Timeframe: 12/15/2017 - 12/18/2017

Hillsdale College recently conducted a calendar year end campaign that focused on their unique independence from government funding. During the month of December, they sent appeals that focused on different initiatives they are advancing to secure education and restore constitutional liberty in America. In their fourth email appeal, they highlighted Imprimis–their popular monthly speech digest that has a wider readership than the Wall Street Journal. Before sending this appeal, they wondered: Will increasing the relevancy of the subject line increase email open rate? They created a treatment version with the words ‘Fake News’ and launched an A/B test to find out.

Research Question

Will increasing the relevancy of a subject line increase email open rate?


C: Control
T1: Treatment 1


Treatment Name Open Rate Relative Difference Confidence
C: Control 37.5%
T1: Treatment 1 40.8% 8.8% 100.0%

This experiment has a required sample size of 1,684 in order to be valid. Since the experiment had a total sample size of 40,822, and the level of confidence is above 95% the experiment results are valid.

Flux Metrics Affected

The Flux Metrics analyze the three primary metrics that affect revenue (traffic, conversion rate, and average gift). This experiment produced the following results:

    8.8% increase in traffic
× 0% increase in conversion rate
× 0% increase in average gift

Key Learnings

Hillsdale College found that the treatment version did increase email open rate by nearly 9%. It’s clear that the use of the term ‘Fake News’ attracted more attention, and therefore, increased motivation of the email recipients. This is important to remember when crafting subject lines during anytime of the year, but especially during a calendar year end campaign. Email recipients are flooded with emails during the last month of the year, and it’s easy to get lost in the shuffle. You can increase your email open rates by using terms that recipients immediately recognize and have an interest in, as long as they are directly related to the topic you are discussing in the email copy.

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Experiment Documented by...

Kevin Peters

Kevin is the Chief Technology Officer at NextAfter. If you have any questions about this experiment or would like additional details not discussed above, please feel free to contact them directly.