B
Evidence Grade B
Graded
under review
Safe to Cite
Current
45%
45% -- open rate lift for Email subject lines (20-40 characters) (2026)
Attribution:
View source
Lighthouse Research Team
Last verified:
·
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Source verified
Evidence graded
Value
45%
Unit
Percentage
Data Vintage
2026
Entity
Evidence Quality
B
Strong, reliable evidence
Sourced from a well-regarded research firm or industry leader with transparent methodology and a reasonably large sample.
Single source - not yet corroborated
Score breakdown
Extraction
75
Source Trust
60
Citation Chain
20
Independence
30
Methodology
45
Freshness
95
Source
verticalresponse.com
Primary
Tier B
http://www.verticalresponse.com/about/news?page=10 ↗
Source Article
In the News
Original Research
verticalresponse.com
· Original study ↗
Methodology
Subject lines between 20 and 40 characters increase open rates by 45%; original study not named in article.
Methodology documented
Segmentation
Industrymarketing
Cite this stat
Plain Text
Email subject lines (20-40 characters): 45% open rate lift. Source: verticalresponse.com (2026). Via Lighthouse Intelligence -- https://lighthousedata.io/data/subject-line-length-open-lift
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<blockquote cite="https://lighthousedata.io/data/subject-line-length-open-lift" style="border-left:3px solid #2563eb;padding:12px 16px;margin:16px 0;font-family:system-ui,sans-serif;background:#f0f4ff;"><strong>45%</strong> -- open rate lift for Email subject lines (20-40 characters)<br><small>Source: verticalresponse.com (2026) · <a href="https://lighthousedata.io/data/subject-line-length-open-lift" target="_blank" rel="noopener">Lighthouse Intelligence</a></small></blockquote>
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