|
|
| GeoCommunity Mailing List |
| |
| Mailing List Archives |
| Subject: | RE: GISList: Census Data Questions |
| Date: |
12/27/2001 03:35:46 PM |
| From: |
Kent Hargesheimer |
|
|
Hi Helen -
I am with SRC, we own the FreeDemographics.com website. Some answers to
your questions from our head Tech person...
1) Many blocks have 0 population. Many of these can be understood by
looking at the land and water area of the block, because often water areas
are put into there own blocks to make the mapping and pop density stuff make
more sense.
2) There are many reasons why population by race can add up to more than
100%. The most common is from looking at population of 1 or more race. Any
1 person can be represented in up to all 6 categories. Also, sometimes
people look at hispanic as a separate race, where in reality it is an
additional variable on top of race. All hispanic people counts as white and
hispanic or black and hispanic, etc... Lastly, if the error is small as in
this question, it is very possible that round off
error in producing whole # percentages has cause the numbers to not add up
to 100.
FreeDemographics.com offers Census 2000 reporting, however, it does not
allow you to download data for mapping in GIS formats like ArcView or
MapInfo. Some additional information that might be helpful to you and other
Census data users out there...
You should also know about DemographicsNow.com, which also has the released
Census 2000 data down to block level up on the web for reporting and
interactive mapping down to block group.
The Census Bureau is bundling SRC's Allocate Data Retrieval Engine (under
the Census 2000 Data Engine name) with the CD & DVD deliveries of Census
2000. This bundling with the software is starting with the national SF1 DVD
(to be released very soon) and will continue through all CD and DVD
deliveries of SF2, SF3, and SF4 over the next few years. The Census Bureau
CDs start at $50 each, DVDs are $70 each with some discounts for larger
volume orders.
SRC is offering some product enhancements (for example, so data can be
extracted already linked to Census 2000 boundaries in MapInfo or ArcView
formats) which can be used with all the Census 2000 data releases. SRC is
even offering the Allocate Data Retrieval Engine API for GIS developers, so
you can make the data available on the web, in the standard delivered format
immediately as it is released. These enhancements will save you (and the
rest of the GIS community who uses this data) a TON of time and money.
See our Census 2000 add-on website
http://www.extendthereach.com/census_add_on for more details on all the
available add-on options. Don't hesitate to contact SRC at 1-888-836-4274
or via e-mail at census_add_on@extendthereach.com with any further
questions.
Thanks,
Kent Hargesheimer
SRC - Extending the Reach of Micromarketing
603 Chadfield Way NE
Leesburg, VA 20176-4823
tel 703-737-7739 fax 703-737-7719
cell 571-213-9459
http://www.extendthereach.com
-----Original Message-----
From: Kahn, Helen [mailto:HKahn@VHB.com\
Sent: Wednesday, December 26, 2001 11:18 AM
To: 'gislist@geocomm.com'
Subject: GISList: Census Data Questions
Hi All -
this is not a strict GIS question, but I figure someone out there working
with census data can answer my queries.
Question 1: Is it possible to have blocks with zero (0) population?
Question 2: Why do population by race/ethnic origin percentages total less
than, or greater than 100%? Is this an issue of rounding? Or does it have
to do with people identifying themselves as more than one category, i.e.,
Black & Hispanic Origin?
Here's the background to my question:
I downloaded population by race data from FreeDemographics.Com. The tabular
data are reported as total population and then percentages of each race for
each block The categories are Whites, Blacks, American Indian,
Asian/Pacific Islander and Hispanic Origin. I am looking at an area in
Connecticut around a highway interchange, and I am looking at the block
level. I am using the 2000 Census Summary File 1. Several of the blocks in
this area report 0 for total population. In some of the blocks that do
report populations, the percentages of race/hispanic origin add up to 100
+/- 2%.
Any information would be appreciated.
thank you.
Helen
To unsubscribe, write to gislist-unsubscribe@geocomm.com
________________________________________________________________________
Setup a GeoCommunity Account and have access to FAST DataDownloads
and Premium Career Posting at a discounted rate!
https://www.geocomm.com/cgi-bin/accounts/login
On-line Archives available at
http://spatialnews.geocomm.com/community/lists/
To unsubscribe, write to gislist-unsubscribe@geocomm.com
________________________________________________________________________
Setup a GeoCommunity Account and have access to FAST DataDownloads
and Premium Career Posting at a discounted rate!
https://www.geocomm.com/cgi-bin/accounts/login
On-line Archives available at
http://spatialnews.geocomm.com/community/lists/
|
|
Sponsored by:
For information
regarding
advertising rates
Click Here!
|
