| County | Rank | Change (2020) ↓ | 2026 Pop. | 2020 Pop. |
|---|---|---|---|---|
| Greater Bridgeport Planning Region | 1 | 4.51% | 339,003 | 324,360 |
| Western Connecticut Planning Region | 2 | 3.96% | 643,243 | 618,740 |
| Capitol Planning Region | 3 | 3.63% | 999,036 | 964,034 |
| Naugatuck Valley Planning Region | 4 | 3.61% | 465,218 | 448,993 |
| Northeastern Connecticut Planning Region | 5 | 3.52% | 98,565 | 95,212 |
| South Central Connecticut Planning Region | 6 | 2.75% | 579,944 | 564,449 |
| Northwest Hills Planning Region | 7 | 2.58% | 115,100 | 112,206 |
| Lower Connecticut River Valley Planning Region | 8 | 2.49% | 177,575 | 173,266 |
| Southeastern Connecticut Planning Region | 9 | 2.33% | 284,859 | 278,383 |
Connecticut's counties show varied growth patterns from 2020 to 2026. Greater Bridgeport Planning Region leads with 0.74% annualized growth, followed by Western Connecticut Planning Region (0.65%) and Capitol Planning Region (0.6%). The largest counties are Capitol Planning Region (999,036), Western Connecticut Planning Region (643,243), and South Central Connecticut Planning Region (579,944). All 9 counties in Connecticut are growing. Overall, counties averaged 0.54% annualized growth, with total population growing by 0.56% annually.
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