[1] He took an interest in sociological questions even as a young man at the École des Mines, befriending a follower of the socialist thinker Saint-Simon.

[2] For nearly a quarter of a century Le Play travelled around Europe, collecting a vast amount of material bearing on the social and economic condition of the working classes.

In 1855, he published Les Ouvriers Européens (The European Workers), a series of 36 monographs on the budgets of typical families selected from a wide range of industries.

Emperor Napoleon III, who had met Le Play in Russia during his travels across Europe in the 1840s and held him in high esteem, entrusted him with the organization of the Exhibition of 1855.

The following year Napoleon III appointed Le Play to the Council of State, the legislative assembly of the Second French Empire, where his official duties included overseeing numerous industries.

At the prompting of the Emperor, Le Play published his recommendations for improving French society in his work Social Reform in France (1864).

[4] At about the same time in France, legal history academics working on customary law were the first to re-apply Le Play's methods in scientific research.

[5] In the early 1970s, a growing number of ethnologists and historians joined this trend, especially those within the historical anthropology school: André Burguière, Emmanuel Le Roy Ladurie.

[10] At the end of the 1970s historian and demographer Emmanuel Todd, a disciple of both Emmanuel Le Roy Ladurie and Peter Laslett, was struck by the geographical similarity between the area of prevalence of the communitarian family system (patriarcal family in Le Play's words) and the regions where communism had become dominant in the 20th century.