Hi, my name is David Kraiker.
I work at the United States Census Bureau as a
Data Dissemination Specialist.
For many years, I worked as a geographer,
and today what I'm going to do is I'll
walk you through this presentation, explaining to you
statistical geographies that we use at the Census Bureau
and which might help you
find your data.
A couple of things
while we go through this presentation.
One, I will take you on a little bit of a field trip at one point,
and another point,
I want you to look for what I call a "lagniappe."
A lagniappe is sort of like a little bonus, a little present that we give you
for you to get something extra out of this, so
look for that lagniappe as we're going through this.
It'll help spark your interest.
So,
this module covers statistical geographies.
It's part of a larger
presentation called "The Ins and Outs and Whereabouts of Census Geography,"
but let's look to the right here and think about what we will look through today.
We will look at Census block,
the block group,
tract,
designated place, Census Designated Places, sometimes I like to put a hyphen in there,
Census County Divisions,
Metropolitan and Micropolitan Statistical Areas, we call those "MSAs,"
Public Use Micro Data Areas, those are also called "PUMAs,"
and Zip Code Tabulation Areas," and we do call those "ZCTAs."
What is a statistical geography?
It's an area of interest used for understanding statistics
and numbers that is created when administrative,
or legal geographies are unavailable or insufficient.
Let's move on here. This is what we call our
"hierarchy" at the Census Bureau, and we actually are going to
look at the ones that I've bolded here
in this blue, dark blue color.
We're moving up the ladder today, or up the hierarchy, so we
start at the bottom with block,
and block nests within block groups,
and tract
nests within that.
And then notice things, for example, at the upper left, ZCTAs actually nests within the nation.
So
just keep that in mind.
I know that's kind of a hard thing, but we do have this little hierarchy.
So let's think about the Census block.
We look over here on the right,
we have an area.
This is block 1,000.
There's a river on the left.
There is a railroad on the right.
It is the smallest geographic area that we present data for.
Usually that's for decennial.
For other things, we're going up higher on the food chain.
These are the building blocks for everything.
They are bounded by these little features, or survey features,
and they often correspond to city blocks.
And so that is something to keep in mind as we move along here.
Hi, we're out here today.
We're looking -- going to be walking around this block.
As you can see behind me, there's a huge carpark,
but we're actually going to go up that street
and walk around this block really quickly,
and I want you to remember a couple things about Census blocks.
They are self-contained,
so we like to begin at one spot,
walk around the block,
or drive around the block,
and end up where we started.
There are usually things you can see on the ground
or they could be survey boundaries.
And then the other thing is that we are actually --
a Census block is actually something we created to capture the potential, the population potential.
So
that means that perhaps nobody is actually living here right now
or hasn't built a house,
but they may someday.
And so that is part of the reasoning behind these sort of self-contained
blocks to whole population.
All right, let's take a walk.
Okay, here we are the corner.
We're going to start walking up the street really quickly
and then we're going to turn the corner.
Oh, those are nice homes.
Keep going.
Turn the corner again.
Oh, man, look at that tree,
down the street
and around the corner,
lots of homes, but over here there are a few apartments.
We keep going,
and then we get to our carpark again and back to square one.
That was a block.
So let's look at this, a block group.
A block group is actually a subdivision of a Census tract.
It is a way to present data and control block numbering.
We do have sort of a range for block codes.
There's some limited data available at the block group level and it is the smallest
unit for sample data, meaning data coming from ACS,
and it is one thing we have participants participating
with us every 10 years renumbering their block groups, if they see fit.
We also have this thing called the "Census tract"
and this is really the showcase geography that the Census Bureau has developed.
Developed that back and released it nationwide back in 1940.
It's very permanent, meant to be used temporally.
It's created for presenting statistical data.
The boundaries are often visible features that you can see on the ground,
but they could be survey boundaries as well.
Around the country, there are about 4,000 people in a Census tract,
and so this is a very good way to analyze demographic data if you need to look at that.
But we also have to think about this.
Since I said we have 4,000 people in a Census tract,
what happens if the Census tract swells up in population?
And so at that point, we're going to have to divide a Census tract, right,
and we would take Tract Number 125
and then that would become 125.01 and 125.02.
If you were looking at this not on a map but on a list or chart,
you probably are going to have to go looking for a geography crosswalk,
which we do supply,
and you can figure out what things have changed going back through time.
So something just to keep in mind as you're looking and working with Census tract.
So have this thing called a Census County Division,
and that was on that hierarchy, right,
and this is part of a county.
This map is not the easiest thing to read over here on the right,
but it is a subdivision of a county where we do not have minor civil divisions,
so where we don't have townships or towns,
we have created in those states Census County Divisions.
They are not widely understood in many of those counties,
but it is a way for you to analyze your county
with a wall-to-wall coverage of geography
so that, you know,
you can see data for the whole county,
wall to wall,
so one thing just to keep in mind
when you're looking for this sort of information.
We also have this idea of the Census Designated Place.
Like I say, I sometimes like to put a hyphen in there,
but here's a map of Singac, New Jersey.
It's the statistical
counterpart of an incorporated place.
It is not incorporated, but it's a place that looks like probably it should be incorporated.
It is a settlement or a concentration of population,
and we delineated -- Census Bureau delineates it with the county.
Usually every 10 years, we offer that to the county.
There are some places where there are no incorporated places,
Hawaii,
Puerto Rico,
and Guam,
and they only use Census Data Designated Places to get data.
The next thing we have is a Metropolitan/Micropolitan Statistical Areas.
We just call those "MSAs."
That represents both of these types of areas.
So the idea is to have a core area with a large population in it.
Usually that population has to be over 50,000 people.
So here we have on the right Kansas City.
Kansas City certainly has over 50,000 people,
but then around that we have some Micropolitan Statistical Areas and those areas
generally have 10,000 to 15,000 people in them
and they are sort of outlying or surrounding the main area,
so that's something to keep in mind.
It is dependent on decennial population.
The Office of Management and Budget, not the Census Bureau,
delineates these areas after a 10-year Census
depending on population increases and where they see fit.
We also have this thing called the "Public Use Microdata Area"
and it is a good thing to use if we use --
working with ACS data.
We work with state data centers to delineate these,
and there's a threshold of about 100,000 people.
So notice we use the word "micro" or "microdata area" up here
and what that means is, you can get more data.
You're getting smaller
and more precise data if you need that,
but the area gets larger in population.
So over here on the right,
this is a good little diagram here.
It comes from the city of New York.
They have what they call "CDs," community districts,
so Community District 4, Community District 5.
You can see this back here, and that corresponds to PUMA Number 3807.
One thing I will point out,
PUMAs used to be numbered
and now they are named
and that is to help reflect the area that they are within.
So here we have urban areas,
and that's really sort of a collective terminology
and it refers to both urban areas and urban clusters,
but let's just think about this,
and I'm sorry I don't have a better diagram,
but urban areas are actually just densely developed territory.
It has to have at least 50,000 people in it
and usually it's in the vicinity of a larger populated place.
Then we have urban clusters,
and urban clusters are somewhere,
I said at least 2,500 people, but all the way up to 50,000,
and they're sort of surrounding these other urban areas, if you will.
Going forward,
from 2020 Census,
urban areas will no longer be distinguished as either an urbanized area or an urban cluster
all qualifying areas we be designated urban areas,
so look for that change.
Let's move on to Zip Code Tabulation Areas, right?
And so Zip Code Tabulation Areas
are actually approximate.
They actually approximate a five-digit zip code area,
but we actually create these using populations that are primarily in certain zip codes,
but one thing is a lot of people go looking for geographic files,
right,
and Zip Code Tabulation Areas are actually free.
In many other places where you look for that,
you actually have to pay for that data.
So here's where I'm going to give you a little lagniappe,
and if you want to go to
this URL,
you can actually see yours truly giving a little presentation on zip codes,
or Zip Code Tabulation Areas,
and you can get a little bit more information on that.
Why don't we move along?
We've we sort of gone through all those different things,
and let's just have a little quiz here.
So we think about this,
which of these geographies average about 4,000 people and do not cross county lines, okay?
So that is the Census tract.
If you remember earlier, I said
Census tracts are sort of stable in time.
They were created to have about 4,000 people in them,
and as we move through time,
we like to keep those Census tracts in the same place,
but remember, I said
if one swells up in
population,
we will subdivide it
and we will change the numbering scheme,
so something to keep in mind as you go through this.
Okay, our second little quiz here.
Which of these geographies can cross county lines?
And there may be more than one answer.
So the things that can cross county line, right, or actually,
Metropolitan Statistical Areas,
Zip Code Tabulation Areas,
and urban areas,
and so the one thing that got left out there was the block group, okay?
Block groups nest, remember, within tracts.
Tracts nest within the county.