Were our great-grandparents happier than ourselves?

In October Nature Human Behaviour published an article suggesting the British of the late 19th and very early 20th centuries, our great-grandparents, were happier, or at least as happy as the British are today. That's despite the much higher infant mortality and shorter lifespan at that time than now with (the legacy of?) the welfare state.

The article "Historical analysis of national subjective wellbeing using millions of digitized books" is behind a paywall but an earlier pdf version is openly available here. The abstract reads:

In addition to improving quality of life, higher subjective wellbeing leads to fewer health problems, higher productivity, and better incomes. For these reasons subjective wellbeing has become a key focal issue among scientific researchers and governments. Yet no scientific investigator knows how happy humans were in previous centuries. Here we show that a new method based on quantitative analysis of digitized text from millions of books published over the past 200 years captures reliable trends in historical subjective wellbeing across four nations.This method uses psychological valence norms for thousands of words to compute the relative proportion of positive and negative language, indicating relative happiness during national and international wars, financial crises, and in comparison to historical trends in longevity and GDP. We validate our method using Eurobarometer survey data from the 1970s onwards and in comparison with economic, medical, and political events since 1820 and also use a set of words with stable historical meanings to support our findings. Finally we show that our results are robust to the use of diverse corpora (including text derived from newspapers) and different word norms.

The figure shows the steady climb to the late 19th century, a levelling off (corresponding to the period of high immigration), precipitous drops associated with the two world wars. Post WW2 there is a rapid rebound although a considerable difference between the index based on books and that based on periodicals.

The article shows similar data for the US, Germany and Italy.

It would be interesting to see if the trends could be reproduced by analysis of letters and diaries.