Who are Sonoma County's voters?

Heading into Tuesday's presidential primary, the political landscape of Sonoma County is dominated by Democrats, making this a blue county in one of nation's bluest states.

An analysis of Sonoma County voter rolls also found that there are fewer voters than 10 years ago and that younger voters are most likely to register as independents.

Republicans have lost ground since 1998. However, some of the largest GOP numbers are in Windsor, one of the county's fastest-growing cities.

And Republican registration grows steadily with age, with the biggest numbers among voters in their 60s and 70s.

The largest concentration of Democrats -- and the largest bloc of voters -- is people in their 50s. The biggest strongholds are in the west county.

Land of Democrats

Democrats abound in the rolling green hills and along the Russian River in west Sonoma County.

They account for more than 60 percent of registered voters in five communities: Villa Grande, Graton, Monte Rio, Guerneville and Occidental, according to a Press Democrat analysis of the 2008 county voting rolls.

Of the 12 communities in which Democrats are 55 percent of the electorate or more, all but two -- Glen Ellen and El Verano -- are west of Highway 116.

Democrats enjoy a 2-to-1 advantage over Republicans (51.2 percent to 25.1 percent) among Sonoma County's 231,748 registered voters. The ratio is similar in the three largest cities -- Santa Rosa, Petaluma and Rohnert Park.

Republicans are in the minority almost everywhere. The county had 70,439 registered Republicans, or 30.3 percent of the electorate, in 1998, compared with 58,101 voters now.

Fulton is the only community in Sonoma County where Republicans outnumber Democrats, 39.8 percent to 36.6 percent, out of only 314 voters.

Republicans account for more than 30 percent of voters in only two other places: Windsor (31 percent) and Geyserville (30.3 percent).

There are 915 fewer registered voters in the county this year (231,748) than there were in 1998 (232,663), even though the population grew 9 percent in the past decade.

Since 1998, county elections officials have implemented an "inactive file" for voters whose ballot materials are returned to the county by the post office. They remain eligible to vote, but are no longer listed on the active voter rolls, said Karen Castor, an election services supervisor.

There are about 139,000 people in the inactive file, which may explain why the rolls appear to have shrunk, she said.

The number of voters registering as independents, officially listed as "declines to state," has swelled by 61 percent in the past 10 years. There were 25,931 independents in 1998, or 11.1 percent of the total; now there are 41,827 independents, 18 percent of the electorate.

Independents are spread pretty evenly around the county, with concentrations of 20 percent or more in Duncans Mills, Rio Nido, Annapolis and Rohnert Park.

Green Party registration ranks fourth in the county (behind Democrats, Republicans and independents) but totals just 2.3 percent. Green ranks have grown by 54 percent in the past 10 years.

American Independents account for 2 percent of county voters.

All other parties, including Libertarian, Peace and Freedom, Reform and Natural Law, have less than 1 percent.

All about the 50s

Fiftysomethings are the most numerous and most liberal, or at least the most heavily Democratic, of Sonoma County voters.

Dividing the population into six age groups -- under 30, 30-39, 40-49, 50-59, 60-69 and over 70 -- Democratic registration rises steadily to the 50s, peaking at 57.3 percent, then drops slightly but remains above 50 percent among the 60s and over 70s.

Republican registration grows almost steadily with age, from 15.9 percent for under 30s to 36.7 percent for the over 70s, according to a Press Democrat analysis of the 2008 county voter rolls.

Among the 50s, by far the largest age bloc in the county, GOP registration is 22.7 percent.

There are 54,532 voters in their 50s, more than 10,700 greater than the 40s bloc, the second-largest.

Independent registration is the mirror image of Republicanism, steadily declining with age.

Nearly a third of voters under 30, or 32.8 percent, have declined to name a political party, but the level drops to a fourth (25.1 percent) of voters in their 30s and to less than one-fifth (18.9 percent) of voters in their 40s.

Fewer than 8 percent of voters over 70 are independents.

Ten years ago, the age profile of county voters was largely the same as now.

Independents were far less numerous in 1998, with 19.5 percent of voters under 30 declining steadily to 5.3 percent of voters over 70.

Voters from all over

A majority of Sonoma County voters, 56 percent, or nearly 130,000, are native Californians.

Of currently registered voters born outside the Golden State, the largest number comes from New York (8,233, or 3.6 percent), followed by Illinois (5,507, or 2.4 percent).

Voters born in Mexico number 5,075, or 2.2 percent of the electorate. All registered voters are U.S. citizens.

There are 7,588 registered voters who listed the United States, but did not specify a state, as their place of birth.

Nine states -- Pennsylvania, Washington, Michigan, Texas, Ohio, Oregon, Massachusetts, New Jersey, and Minnesota -- have native sons and daughters accounting for 1 percent to 2 percent of county voters.

The voting rolls have a genuinely international flavor, including people born in Germany (1,410), Canada (1,086), Philippines (998) and England (817).

Smaller numbers hail from China, El Salvador, Japan, Vietnam, United Kingdom, Italy, France and India, to name a few.

There are 24 voters from Iraq; 22 from Afghanistan.

Twenty-four nations have a single native on the voting rolls, including Armenia, Mongolia, Rwanda, Seychelles, Cocos Islands and Cayman Islands.

Staff Researcher Michele Van Hoeck contributed to this article. You can reach Staff Writer Guy Kovner at 521-5457 or guy.kovner@pressdemocrat.com.