| | Spring Lake township, MI | Saugatuck township, MI | United States |
| Population | 15,266 | 3,404 | 329,725,481 |
| Female Population | 50.5% | 48.0% | 50.5% |
| Male Population | 49.5% | 52.0% | 49.5% |
| Median Age | 46.8 | 50.7 | 38.4 |
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| Population - 2010 | 14,308 | 2,951 | 309,327,143 |
| Population - 2000 | 13,140 | 3,590 | 285,036,114 |
| Population - 1990 | 10,751 | 2,916 | 251,960,433 |
| Pop. 2000 to Now | 15.5% | -5.1% | 15.6% |
| Pop. 1990 to Now | 41.2% | 16.9% | 30.8% |
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| Population Density | 926.5 | 145.6 | 93.4 |
| Land Area | 16.5 | 23.4 | 3,531,905.4 |
| Water Area | 2.3 | 0.8 | 264,836.8 |
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| Est. Total Population By Age | | | |
| | Spring Lake township, MI | Saugatuck township, MI | United States |
| Age 0 to 4 | 5.2% | 2.6% | 5.9% |
| Age 5 to 9 | 7.6% | 7.5% | 6.1% |
| Age 10 to 14 | 5.3% | 5.9% | 6.6% |
| Age 15 to 17 | 3.0% | 2.5% | 3.9% |
| Age 18 to 20 | 2.1% | 2.8% | 4.0% |
| Age 21 to 24 | 4.0% | 3.4% | 5.2% |
| Age 25 to 34 | 8.8% | 6.4% | 13.8% |
| Age 35 to 44 | 12.2% | 10.1% | 12.9% |
| Age 45 to 54 | 14.1% | 16.0% | 12.6% |
| Age 55 to 59 | 8.2% | 8.6% | 6.7% |
| Age 60 to 64 | 6.3% | 7.1% | 6.3% |
| Age 65 to 74 | 14.0% | 19.7% | 9.6% |
| Age 75 to 84 | 7.0% | 7.4% | 4.5% |
| Age 85 and over | 2.2% | 0.0% | 1.9% |
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| Race | | | |
| | Spring Lake township, MI | Saugatuck township, MI | United States |
| White | 93.4% | 86.1% | 59.4% |
| Black | 1.2% | 0.2% | 12.2% |
| Asian | 0.9% | 0.5% | 5.6% |
| Native American | 0.1% | 0.9% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.2% | 0.0% | 0.4% |
| Two or More Races | 2.2% | 1.7% | 3.2% |
| Hispanic | 2.1% | 10.5% | 18.4% |
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| Marriage & Family | | | |
| | Spring Lake township, MI | Saugatuck township, MI | United States |
| Married Population | 62.2% | 72.5% | 49.8% |
| Currently Married | 61.0% | 72.5% | 48.0% |
| Married but Separated | 1.2% | 0.0% | 1.8% |
| Single Population | 37.8% | 27.5% | 50.2% |
| Never Married | 21.3% | 15.3% | 33.8% |
| Divorced | 11.5% | 8.0% | 10.8% |
| Widowed | 5.0% | 4.3% | 5.6% |
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| Household Size | 2.25 | 2.46 | 2.60 |
| Households | 6,720 | 1,386 | 124,010,992 |
| Family Households | 4,292 | 1,045 | 80,755,759 |
| Married couple, w/children | 29.7% | 26.3% | 30.5% |
| Married couple, no children | 56.3% | 70.8% | 42.9% |
| Non Family Households | 2,428 | 341 | 43,255,233 |
| Single householder, w/children | 6.0% | 0.0% | 15.8% |
| Single householder, no children | 8.0% | 2.9% | 10.8% |