Monthly Archives: July 2012

Pitfalls of Working with Census Data

Posted by Ezra Glenn on July 27, 2012
Census, Missions, Reconnaissance, Shape Your Neighborhood / No Comments

Previous missions have demonstrated a whole lot of things you can do with census data. Here are a few of the problems you can get yourself into.

Census Geography Pitfalls

  • Unequal tracts: Despite what you may think, not all Census tracts (and their composite block groups and blocks) are created equal. The Census Bureau tries to structure their geography so that all tracts will be approximately the same size (about 4,000 people), but in practice there is a pretty large range (between 1,500 and 8,000 people per tract). If you are looking at raw numbers (counts of any sort), be sure to think about the overall population—it’s the denominator you’ll need to put the figures in perspective; conversely, if you are looking at percentages, remember that a small percentage of a large tract could actually be more people than a large percentage of a very small one.
  • Overlapping districts: Unfortunately, although the formal “pyramid” of Census geography is well-structured—building from block to block group to tract and so on up—our political and cultural divisions are not always so straightforward: cities sometimes spread across county lines, metropolitan areas may even cross state lines, and legislative districts have become a gerrymandered mess that would drive any rational cartographer to drink. As a result, there may be times when Census geographers have been forced to choose between a strictly “nested” geography that ignores higher-order political elements, and one with intermediate levels that do not fit neatly within each other.
  • Confusing or ambiguous place names: Partially related to the previous point, and partially due to the general orneriness of the culture (or perhaps the species), there are often times when the same name will occur in multiple places in Census geography. The name “New York” refers to a state, a metro region, a city, a county (strangely, one that is smaller than its city), and even an avenue in Atlantic City (or on the Monopoly Board). Luckily, once you get down to the level of census tracts and below, you enter the realm of pure-and-orderly numbers, and can largely avoid this trap—they are even sometimes referred to as “logical record numbers,” or LOGRECNO—although it’s a lot less fun to say “AR census tract 9803 block group 3” when you could be saying “Goobertown, Arkansas”.
  • Changing boundaries: Occasionally the Census Bureau needs to redraw the lines for some particular location—perhaps a city has annexed new land, or a large county has been split by an act of the state legislature. In these situations, you may see a sharp rise (or drop) in the counts from one Census to the next. For example, according to the 2000 census, the city of Bigfork, Montana had 1,421 people; in the 2010 census, this figure had grown to 4,270—a seeming tripling of the population. However, upon closer scrutiny, it turns out that most of this increase was the result of a change in census boundaries. (These situations may also exacerbate some of the previous problems.)

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Freedom of Information: Public Records Requests

Posted by Ezra Glenn on July 20, 2012
Missions, Reconnaissance, Shape Your Neighborhood / No Comments

Many of the “reconnaissance” missions found here either explore some existing public database (such as the Census, via FactFinder), or demonstrate innovative tools to gather new data for your planning efforts. Sometimes, however, you will be interested in making use of information contained within City Hall or some other public agency, but it is not entirely clear how to gain access it. When access to information is the problem, it is important to understand the notion of public records and the proper application of the “Federal Freedom of Information Act” (and any parallel state legislation).

What the law says

President Lyndon B. Johnson signed the Freedom of Information Act (known as FOIA) into law — appropriately, albeit somewhat ironically, given the players involved — on July 4, 1966, thereby establishing a consistent process under which citizens could enforce their right to access government records. Importantly — as legal scholars and civil rights advocates will be quick to note — the right itself existed prior to the Act: in a democratic society, public records are already public, and we have every right to view them, copy them, analyze and distribute them, and otherwise be as nosy as we want to be. Remember: it’s government of the people by the people, and we shouldn’t be shy about asking what it’s up to even when it operates behind closed doors.

Over the past five decades, FOIA requests under the act have become a standard step in investigative journalism, citizen government accountability movements, and even high-profile lawsuits. Nationwide, more than 500,000 requests are made each year, resulting (eventually — see below) in one of the most abundant sources of information about an astonishing array of topics, from arrest records to political campaign spending, from tax assessments to high-school drop-out rates, and so on.1

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