Is Cos Cob, CT growing?

Name: Growth in Cos Cob, CT, 2020–2024
Creator: US Census Bureau
License: https://www.census.gov/data/developers/about/terms-of-service.html

Cos Cob, CT had an estimated 7,546 (±960) residents in 2020–2024, against 6,990 in 2015–2019.

That is a change of +8.0%, not a measurable change.

Its housing went from 2,626 to 2,836 homes (+8.0%), not a measurable change.

0.0% of today’s homes were built in 2020 or later.

Figures last updated on November 12, 2026.

Residents now: 7,546 (±960)
Amount of change: +8.0%
Homes change: +8.0%
Built 2020 or later: 0.0%

Residents and homes in Cos Cob, 2015–2019 and 2020–2024

2015–2019 and 2020–2024 American Community Survey 5-year estimates
	2015–2019	2020–2024	Amount of change	Verdict
Residents	6,990 (±397)	7,546 (±960)	+8.0%	Not a measurable change
Housing units	2,626 (±113)	2,836 (±287)	+8.0%	Not a measurable change
Households that rent	31.5% (±5.7 points)	33.3% (±7.9 points)	+1.8 percentage points	Not a measurable change
Median gross rent	$1,979 (±$243)	$3,067 (±$701)	+55.0%	No measurable change after inflation
Median home value	$1,055,400 (±$61,052)	$1,210,400 (±$136,068)	+14.7%	No measurable change after inflation

The Census Bureau publishes 2015–2019 dollars in 2019 dollars and 2020–2024 dollars in 2024 dollars.

Prices (the CPI-U, US Bureau of Labor Statistics) rose 22.7% between 2019 and 2024, so a dollar figure’s verdict compares the two after raising the earlier one by that much, using the Census Bureau’s test for a difference.

The two periods do not overlap, as the Census Bureau recommends for 5-year estimates.

Growth in Cos Cob against Western Connecticut Planning Region, its state and the nation

Change between 2015–2019 and 2020–2024
	Residents	Verdict	Housing units
Cos Cob	+8.0%	Not a measurable change	+8.0%
Western Connecticut Planning Region	—	—	—
Connecticut	+1.4%	Measurable increase	+1.7%
United States	+3.1%	Measurable increase	+4.6%

A change in a place’s boundaries between the two periods (an annexation, say) changes its counts as well; the Census Bureau’s figures are for the place as it was drawn in each period.

New homes in Cos Cob

Housing units by year built, 2020–2024
Year built	Cos Cob	Western Connecticut Planning Region	Connecticut	United States
2020 or later	0.0% (±1.5 points)	1.0%	0.7%	2.0%
2010 to 2019	9.2% (±4.4 points)	8.2%	4.5%	9.4%
2000 to 2009	2.5% (±1.9 points)	8.9%	7.1%	13.6%

9.2% of the homes in Cos Cob were built in 2010 or later.

The median age of residents is 39.6 years.

Growth in places near Cos Cob

Change in residents between 2015–2019 and 2020–2024
Place	Distance	Residents now	Amount of change	Verdict
Cos Cob	—	7,546	+8.0%	Not a measurable change
Riverside	1.3 mi	8,954	+4.1%	Not a measurable change
Greenwich (community)	2.3 mi	14,792	+11.3%	Measurable increase
Old Greenwich	2.3 mi	6,936	+1.3%	Not a measurable change
Stamford	3.2 mi	137,144	+6.1%	Measurable increase
Glenville	3.9 mi	2,656	+4.6%	Not a measurable change
Pemberwick	4.0 mi	3,665	−10.2%	Not a measurable change
Byram	4.6 mi	4,633	+1.6%	Not a measurable change
Village of Port Chester	5.0 mi	31,102	+6.0%	Measurable increase

Cos Cob is a census-designated place: an unincorporated community the Census Bureau draws for statistics, with no municipal government of its own.

It lies inside Greenwich, whose figures include it.

Survey years: 2020–2024 (American Community Survey 5-year estimates), compared with 2015–2019.

Margins of error are at the 90% confidence level.

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Questions about Cos Cob

Is Cos Cob growing?

Cos Cob, CT had an estimated 7,546 residents in 2020–2024 and 6,990 in 2015–2019, a change of +8.0%: not a measurable change by the Census Bureau’s test.

How many homes have been added in Cos Cob?

The estimated number of housing units went from 2,626 in 2015–2019 to 2,836 in 2020–2024 (+8.0%), not a measurable change.

How much new construction is there in Cos Cob?

0.0% of homes in Cos Cob were built in 2020 or later and 9.2% between 2010 and 2019.

Sources

To check these figures in the Census Bureau’s own API, request the variables below from the 2024 ACS 5-year data profile (acs/acs5/profile) for Cos Cob CDP, Connecticut (place:17520, in state:09).

Each estimate (E or PE) has a margin of error beside it (M or PM).

The 2015–2019 figures are B01003_001E, B01003_001M, B25001_001E, B25001_001M, DP04_0047PE, DP04_0047PM, B25064_001E, B25064_001M, B25077_001E, B25077_001M from the 2019 release.

The API needs a free key.

Request a Census API key.

DP05_0001E, DP05_0001M, DP04_0001E, DP04_0001M, DP04_0017PE, DP04_0017PM, DP04_0018PE, DP04_0018PM, DP05_0018E, DP05_0018M

This product uses the Census Bureau Data API but is not endorsed or certified by the Census Bureau.

Figures are published by the US Census Bureau, HUD, the Bureau of Labor Statistics and the FBI; Seayora reproduces them and does not adjust them, except where a sentence says it compares dollar figures after inflation. They describe the whole place, not any one building or street, and are not an appraisal, a rent determination, a tax bill, a safety rating or legal advice.