1.1% of homes are flats, below 99% of compared French towns
In the typical compared French town, 14% of households are headed by a manual worker; in Lachy, 24%. Locally, 5.6% of households have no car. Few places have as many second homes: 5% here, more than in 77% of compared French towns. The 2023 Census counted 345 residents in 160 households.
Throughout this page, the Marne median and the France median are the median of compared communes (those with an overall grade), each figure its own median. Source: INSEE, census 2023.
+11% since 2012, a pace 73% of compared French towns didn’t match
Residents at INSEE’s last three censuses, each recast in the 2026 commune boundaries. France has no yearly estimate by commune between censuses.
2012 to 2023
2017 to 2023
For comparison, the median compared French town changed +5% and the median Marne town −2%. The first five years brought +7%; the six to 2023, +4%.
Older than 75% of compared French towns: half of Lachy is over 48.1
Shares of residents by age at the 2023 census.
Age groups · share of residents
Median age of the 3,798 compared French towns
■ Lachy 48.1. The median compared French town: 44.
Residents aged 15 to 24 make up about one in ten here (10%). On residents aged 65 and over, Lachy sits higher than 57% of compared French towns: 23%.
Women and men · all residents
53% women, 47% men
About 89 men for every 100 women. Median share of women: Marne 52.7%, France 51.8%.
A smaller share of one-person households than 73% of compared French towns: 31%
A household is everyone who shares a main home (résidence principale). Household types come from INSEE’s fuller sample of a quarter of census forms.
Against the Marne median and the France median
Living alone · share
With single-parent households at 12%, Lachy is ahead of 78% of compared French towns on that count. Each household has 2.1 people on average. More couples with children than in nearly three fifths of compared French towns: 27%. The benchmark for one-person households in the typical compared French town: 35%.
Fewer empty homes than 74% of compared French towns: 5%
Every home the census counted: main residences, second homes and occasional dwellings (INSEE counts them together), and empty homes. Owning and renting are on Cost of living.
All homes · share of homes
Type of home
Cars per household · share of households
Households in social housing are rarer here than in 99% of compared French towns. Set beside that, 6.7% of homes stand empty in the typical compared French town. Turnover: 6.8% of households moved in less than two years ago, and 25% have lived in their home 30 years or more.
A median standard of living of €29,120 a year
The standard of living (niveau de vie) is a household’s disposable income after taxes and benefits, divided by its consumption units (UC) to allow for its size and make-up: 1 for the first adult, 0.5 for each other person 14 or older, 0.3 for each child under 14.
Medians of compared communes. Source: INSEE, Filosofi 2023.
The median standard of living in Lachy is €29,120 a year per consumption unit: higher than in 79% of compared French towns.
Lachy ranks above 83% of compared French towns on households headed by a retired person: 40%
Households by the socio-professional group (PCS) of their reference person, INSEE’s own categories. Jobs and commuting are on the Work & commute page.
Households by reference person’s group · share of households
Households headed by a manager or professional are rarer here than in 99% of compared French towns. Across the comparison, 32% of households are headed by a retired person in the typical compared French town.
Each household is counted once, by the occupation of its reference person (usually the oldest working adult).
Lachy ranks below 86% of compared French towns on immigrants: 2.6%
INSEE publishes two measures, which overlap but aren’t the same. Neither is the UK’s “born abroad”.
Share of residents · census 2023
Immigrant (immigré)
Born abroad, not French at birth. Someone stays an immigrant after becoming French. A French citizen born abroad (for example in Algeria before 1962) is not one.
Foreign national (étranger)
Not a French citizen today, wherever born. A child born in France to foreign parents can be a foreign national without being an immigrant.
Here 1.4% of residents are foreign nationals, where the figure in the typical compared French town is 4.3%. The wider picture: 6.5% of residents are immigrants in the typical compared French town.
INSEE publishes no country of birth or ethnicity by commune in these tables, and the census doesn’t ask about religion.
Married residents make up 46% in Lachy, more than in 75% of compared French towns
Residents 15 and over by how they live: the census asks both the legal status and whether people live as a couple.
Residents 15 and over · share
Single residents: 23% here and 25% in the typical compared French town. In the typical compared French town, 43% of residents 15 and over are married.
Graduates of higher education: 27%, a lower share than 62% of compared French towns
Highest diploma of residents 15 and over who have left education, in French terms: the levels don’t map one-to-one to UK or U.S. ones.
Highest diploma · 15 and over, out of education
21% of adults out of school have no qualification (typical compared French town: 19%). The benchmark for graduates of higher education in the typical compared French town: 30%.
Among 41 French towns of 345 to 2,582 people, the 15th oldest
The 40 compared French towns nearest in population, by median age. Hover for each one’s second homes and immigrants; click for its page.
At the ends of the range sit Villejust (37.2), the youngest, and Prayssac (62.3), the oldest.
3 in 5 nearby towns have a higher median age than Lachy
The nearest towns of 2,500 or more, colored by median age. Source: INSEE, census 2023.
| Town | Median age | 65+ | Second homes | Immigrants |
|---|---|---|---|---|
| Lachy | 48.1 | 23% | 5% | 2.6% |
| Sézanne 4,576 · 3.3 mi | 50.7 | 30% | 3% | 8.3% |
| Montmirail 3,535 · 10.5 mi | 51.3 | 32% | 3.4% | 5.2% |
| Villenauxe-la-Grande 2,605 · 13.9 mi | 41.3 | 22% | 3.5% | 9.4% |
| Blancs-Coteaux 3,080 · 16.9 mi | 51.4 | 30% | 3.9% | 1.9% |
| Romilly-sur-Seine 14,959 · 17.5 mi | 42.8 | 23% | 2.7% | 17% |
Health, work, housing and schools
What this data can and can’t tell you
- Census 2023. INSEE’s census is a rolling survey: a fifth of small communes each year, 8% of homes in large ones each year. “2023” pools the surveys of 2021 to 2025, so the figures describe the town around 2023, not on one day.
- Medians of compared communes. The comparisons are the median of the département’s compared communes and of France’s (those with an overall grade), each figure its own median: not the total for the département or for France, which large cities pull towards their own figures.
- Immigrants and foreign nationals. INSEE’s two measures: an immigrant was born abroad without French nationality; a foreign national isn’t French today. Neither is a count of people born abroad, which INSEE doesn’t publish by commune.
- Second homes. Homes used for holidays or weekends, with occasional dwellings (kept for work, for example), which INSEE counts together. Their owners are counted where they live, not here.
- Standard of living. INSEE’s Filosofi: disposable income per consumption unit, from tax and benefit files, 2023. The poverty rate is the share of residents below 60% of France’s median. Not published for the smallest communes.
- What France doesn’t ask. The French census asks nothing about ethnicity, religion, language or health, so this page has no such section.
Questions about who lives in Lachy
What is the population of Lachy?
345 at INSEE’s 2023 census, 11% more than in 2012 (310).
How old are Lachy’s residents?
The median age is 48.1, older than 75% of compared French towns. 18% are under 18 and 23% 65 or older.
How many second homes are there in Lachy?
9, with occasional dwellings: 5% of all homes, against 2.1% for the median compared French town.
How many immigrants live in Lachy?
INSEE counts 9 immigrants (born abroad, not French at birth), 2.6% of residents, and 5 foreign nationals (1.4%). The medians of compared French towns are 6.5% and 4.3%.
What is the median income in Lachy?
€29,120 a year per consumption unit in 2023 (median of compared French towns €25,970). Source: INSEE, Filosofi.
Sources: INSEE, census 2023 (population, ages, households, homes, marital status, diplomas, immigrants, foreign nationals, employment), 2026 geography · INSEE, Filosofi 2023 (standard of living, poverty) · IGN Admin Express (boundaries) · Medians and percentiles: TownRatings, over compared French towns, updated November 4, 2026. Under the Licence Ouverte / Open Licence 2.0 (Etalab).
Contains public sector information under the Licence Ouverte / Open Licence 2.0 (Etalab): INSEE, DGFiP, the Interior Ministry’s statistics service (SSMSI), the Ministry of Education (DEPP), the Health Ministry’s statistics service (DREES) and the Housing Ministry (Carte des loyers). Commune boundaries: IGN Admin Express.