Tools to analyse subject line lengths over time
Jupyter Notebook Python
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Subject line growth-sqlite-scatter.ipynb

Subject line growth over the years -- a qualitative approach

This code accompanies a blog post at

Summary: I noticed that the subject lines from my inbox circa 1998 seem, on average, shorter than the subject lines of emails I receive today (2016).

In my email corpus, there seems to be a general upward trend in email subject length: the subject line grows, on average, more than one character per year.

Plot showing upward trend of subject line

This means that by the year 2036, the average email subject line will be eighty characters, and no longer be able to fit across an 80-character VT100 terminal. Chaos will ensue.

Here are some tools I wrote to help me conduct this vital analysis:

Program Function Can slurp up and save stats of emails stored in mbox, Maildir or notmuchmail. Can remove personal info (message-ids) from a sqlite3 database created by
Subject line growth-sqlite-scatter.ipynb Create a scatter plot of email subject line length (ipython/jupyter notebook) Plot scatter plot and save as a PNG file from the command line

You'll need the matplotlib libraries to use the script, and Jupyter/ipython to run the ipython notebook. If you want to read mail stored in notmuch, you'll need its accompanying python library.

An example email database (115MB, stripped of personal info) is available separately (torrent)

Questions, queries? Mail me at with the subject line "Hello Danny, I do hope this subject line won't ruin your future averages for any subsequent analysis that you have planned". Thanks!