Big Data on Books:
Decline of Emotional Expression in 20th Century

Study of millions of English language books (using Google Ngram data) finds distinct historical periods of positive and negative moods. Overall, emotion-related words have decreased, except for fear which increased towards the end of 20th century.


A group of researchers from England have analyze trends of 20th century mood words in books, using Google's Ngram database which contains data for over 5 millions books.

The researchers used six standard lists of terms to characterize mood categories: 146 different words that mean anger; 92 words for fear; 224 for joy; 115 for sadness; 30 for disgust; and 41 words for surprise.

Historical periods of positive and negative moods The chart on the right shows difference between scores of Joy and Sadness for years from 1900 to 2000 (raw data and smoothed trend). Values above zero indicate generally 'happy' periods, and values below the zero indicate generally 'sad' periods.

We note that the 1920s were the happiest period, and 1941-43 (WW II period) were the saddest. Happiness went up in 1950-1970, declined thru 1980s and started to increase again in 1990s.

Figure 2. Decrease in the use of emotion-related words through time

The second finding shows a clear decrease in the overall use of mood words through time, with the only exception being Fear (in red) which had the highest final value. Blue line is the trend for Disgust, the emotion with the lowest final value.

To learn more on what that means, see