In-migration to Boulder County rose between 2017-18 and 2022-23

Boulder County · Data as of 2026-10-06 · ALEX Intelligence

Read this carefully: Only counties the IRS disclosed in both vintages, under the same FIPS code and above a minimum flow in each, are compared, because disclosure thresholds move between years and a flow that appears or vanishes at the margin is not evidence that anybody's behaviour changed. Connecticut is excluded throughout: its counties were replaced by planning regions, so no Connecticut geography is comparable across the change. The IRS withholds county-to-county flows below its disclosure threshold, so a county missing from this table is one whose flow was too small to publish, not one nobody moved from. Every total here is a total of disclosed flows and is therefore a floor.

Methodology

Source:

U.S. Internal Revenue Service, Statistics of Income Migration Data, county-to-county inflows, 2017-18 and 2022-23

Measure

Households (change against the earlier vintage), ranked highest first across every U.S. county the IRS recorded sending households to Boulder County (Boulder, Broomfield, CO) in both the 2017-18 and 2022-23 vintages (84 ranked in total).

How the headline figure is computed

Households arriving from the 84 counties the IRS disclosed in both the 2017-18 and 2022-23 vintages: 11,743 against 10,760. Counties disclosed in only one of the two vintages are excluded, because a flow crossing the disclosure threshold is not evidence of movement.

Universe

Every U.S. county the IRS disclosed a flow with. Counties whose flow fell below the IRS disclosure threshold are absent from the source file altogether, so this ranking is of disclosed flows and its totals are a floor rather than a complete count of movers.

Vintage

2023

Reproduce this query

https://www.irs.gov/pub/irs-soi/countyinflow2223.csv https://www.irs.gov/pub/irs-soi/countyinflow1718.csv

Every figure on this page is computed directly from the dataset named above by ALEX Intelligence. No figure on this page was written by hand or by a language model. The query is stated so that anyone can re-run it and obtain the same table.