The number of all residents within the city, as determined by the U.S. Census Bureau.

The number or percentage of the Total Population that is 18 years or older. While these residents are old enough to cast a ballot in U.S. elections, they might not be legally eligible to do so because of citizenship status or other factors (e.g, imprisonment).

The number or percentage of the Voting Age Population (VAP) that is 18 years or older and who are U.S. Citizens. The term "CVAP" is widely used by the Census Bureau; in our study, we also refer to this population as Voting Age Citizens.

The number or percentage of the Total Population with individuals meeting the following three criteria: 1) are 18 years or older as of a given Election Day; 2) hold U.S. Citizenship, and; 3) have not been legally barred from voting for reasons, such as felony convictions. State laws vary widely on this last criterion, and election researchers who use VEP calculations largely do so at the national and state levels, but not for cities.

Given this constraint, whenever feasible our analysis uses Voting Age Citizens as the common denominator for this study.

The number or percentage of the Voting Age Citizen population who have officially registered to vote.

Voter registration rules vary significantly across states, as does the ability of local election officials to update their records in an accurate and timely fashion to reflect such things as address changes, and voters moving to other jurisdictions. In areas with rapid population loss, a jurisdiction may even report a greater number of "registered voters" than there are Voting Age Citizens. For this and other reasons, unless specifically noted, "Voter Turnout" numbers and percentages are based on the number of Voting Age Citizens-registered and unregistered-rather than on the reported number of registered voters.

The number or percentage of Voting Age Citizens who cast a vote in a given election.

A census tract with voter turnout among Voting Age Citizens that is less than 50 percent of the city-wide average. For example, if the citywide voter turnout is 20 percent, a census tract where turnout was 10 percent or lower is considered a Voting Desert.

A census tract with voter turnout among Voting Age Citizens that is at least 150% of the city average. For example, if the citywide voter turnout is 20 percent, a census tract where turnout was 30 percent or higher is considered a Voting Oasis.

The measure of the likelihood of an event given a certain characteristic. For individual census tracts that we’ve mapped for each city, odds ratios are calculated to measure and compare the likelihood that a Older Registered Voter (65 years and older) would cast a ballot compared to a Younger Registered Voter (18-34 years old). This means that Odds Ratios are used as one measure of "electoral clout," which reveals the extent to which a given voter, or group of voters, punches below, at, or above their normal "electoral weight".

A ratio that compares a geographic area to a larger geographic region in which it is situated, according to a specific characteristic, such as patterns of voter turnout. A LQ near 1.0 indicates that voter turnout in the subset geography is comparable to the city average, while values above or below 1.0 indicate the turnout is higher or lower than the city average, respectively.

Mayoral Election Types

Two major systems dominate U.S. Mayoral elections. The most common (used by about 75 percent of U.S. cities) is the Non-Partisan election. Almost all other Mayors, especially in larger cities in the Eastern U.S., are elected in the same type of partisan election system used for electing the President, U.S. Senators, and Governors.

An electoral system where: 1) all candidates compete together; 2) all registered voters receive the same ballot, and; 3) party affiliation is not displayed. In this type of election, if a candidate receives 50 percent or more of the First Round vote, he/she is deemed elected, and no Second Round election is conducted. If no candidate meets this threshold, a Second Round, "run-off" election is held a few weeks or months later, and the winning candidate is elected Mayor.

An electoral system where: 1) a First Round election allows registered voters of separate political parties to choose party nominees, and; 2) names (and party labels) are then part of the Second Round "General Election" ballot. Political party members other than Democrats and Republicans (e.g., Libertarians, Greens) often participate in similar primaries or can attend caucuses to nominate their candidates to the same ballot. The candidate receiving the most votes in the Second Round/General election, though not necessarily a majority, is then elected Mayor.

A voting system that allows voters to rank their preferences in electoral races with more than two candidates in order to avoid the need for a separate "run-off" election should no candidate receive more than 50 percent of "First Preference" votes. Under an IRV system - used for nonpartisan Mayoral elections in St. Paul and San Francisco - the votes for less successful candidates are re-allocated to the top contenders until a winner emerges from the field.

In one case (Palm Beach County), the County Executive is selected by other elected commissioners. In this case, we used election data from the most recent election in which voters elected council members.

If more than one election is used to elect a Mayor, the determinative election is the one deemed by study researchers to be the most important in determining the winner. For the majority of elections with two rounds, the determinative election will be the second (often known as the "run-off") election. However, there are a few exceptions. For Mayoral contests where registered Democrats and Republicans select "party nominees" in the first round, and where registrants of one party overwhelmingly dominate city politics (e.g., in Philadelphia, Democrats outnumber Republicans roughly 10 to 1), the study team determined the first round to be "determinative."

Local Government Types

In this form of government, also referred to as "council-manager", the elected city council (or "Commission" or "Board of Aldermen” [sic]) makes policy and sets the budget of the city. However, to administer city policies and programs, the council then appoints and hires a professional City Manager who is responsible for managing city employees and overseeing the day-to-day operations of the government.

The mayor is a full voting member of the city's policy-making board in these systems, but has little-to-no substantive executive power. Some mayors are simply appointed by their fellow councilors, or the largely ceremonial role is rotated among members. More commonly, the mayor is elected separately, by voters across the entire city. (Council members are often elected from specific districts, though in some jurisdictions they, too, are elected city-wide.)

Elected directly by voters citywide, a "strong mayor" essentially acts as Chief Executive of a city, vested with significant Executive powers to administer the functions and duties of government. This typically includes the power to: appoint and remove department heads; propose annual budgets; and draft and implement administrative rules. "Strong mayors" typically do not serve as voting members on city councils, though they can have legislative powers, too. Some strong mayors have veto power over city council legislation, while others do not. Typically "strong mayors" serve in a "mayor-council" system of government, which consists of an executive branch (Mayor) and legislative branch (City Council).

In addition to possessing legislative power, elected city commissioners in a Commission form of government have executive power and responsibility to administer specific city bureaus and functions. However, the elected Mayor still has significant executive powers in such a system by his/her power to assign and reassign bureaus, including to his/her own portfolio. In our study, only Portland, Oregon has this type of city government.

Census Terms

A U.S. Census measure based on the self-reported income, for one calendar year, of all people living in a single household, regardless of relationship. MHI is the value at which exactly half of the reported household incomes are below, and half of the reported household incomes are above the measure.

According to the U.S. Census, MSAs are regions that have been identified by the Office of Management and Budget (OMB) for statistical purposes. They consist of one urban center of 50,000 residents or more, and the adjoining towns and counties that show a high degree of economic integration with the urban center. For more information, see: http www.census gov/population metro/

The highest level of education that a respondent has completed. In this study, we report educational attainment for adults age 25 years and over, when education has been completed for most people.

The financial agreements that allow for occupation of a home. The most common forms are tenancy, which typically involves renting from a landlord, and owner-occupied housing.