# Presentation: 685972

## ACS Case Studies and Uses

**Linda Gage**
**California Department of Finance**
**Demographic Research Unit **

## Tulare County, California

**Tulare**** County, California**

- Persons in Households
-  361,970
- Housing Units
- 119,640
- Vehicles
- 182,775+

**Notes:**
Tulare County is located in the Central Valley of California.  Tulare County is the second-leading producer of agricultural commodities in the United States. 
The population grew 18 percent since the 1990 census and is projected to increase an additional 52 percent by 2020.  

Over half of the county's population is Latino, compared to 39 percent in 1990, the majority of recent legal immigrants are from Mexico.  

## Attributes with no Statistical Differences by Profile

**Notes:**
In each of the four profiles for San Francisco and Tulare counties in California and in ACS comparison counties across the country, the majority of data values obtained from the 2000 decennial census long-form sample and the average of the 1999-2001 ACS estimates were statistically comparable. 

Though there were differences by profile, overall around 80 percent of the total variables were comparable.   

## Discovered Differences 

-  disability status
-  % vacant housing units
-  age of housing unit
-  number of rooms
-  persons employed
-  median household income
-  high school diploma/no college

**Notes:**
A wealth of Census Bureau research on these differences is available on the Bureau’s website.

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**Notes:**
The differences in the ACS 3-year average estimate and Census 2000 was statistically significant.

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**Notes:**
Percentages are generally more stable and consistent than numeric values.

## Why Would Differences Occur? 

-  questionnaire wording or layout
-  collection mode
- (mail back, telephone, personal visit follow up)
-  residence rules
-  allocation rates
-  controls and weights
-  ACS detecting change
-  seasonal populations
- ACS has no group quarters population

**Notes:**
The American Community Survey has been designed to collect and provide more complete and more current demographic, social, economic and housing information between censuses and to replace the Census 2010 long-form.  The success of this endeavor depends upon continuous and adequate funding, sufficient sample sizes, and a current and accurate Master Address File.  Shortfalls in any of these areas could reduce data quality.  The decennial Census is subject to the same perils.

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## What about Differences? 

- Are statistically significant differences meaningful differences?
- The data are different - is one better?
- How valuable is more current data?
- Can we lessen or explain the differences?
- Can we move beyond the differences and begin to use an ACS time series?

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**Notes:**
The differences in the ACS 3-year average estimate and Census 2000 was statistically significant.

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**Notes:**
The large variety of 250 seasonal agricultural crops attracts seasonal agricultural workers and unauthorized immigrants to the county.  
The California Employment Development Department civilian labor force numbers may be higher because some potential ACS households did not meet the residency rules requirements due to the short-term residence and extreme mobility of those employed in crop harvesting.  
The California employment data reflect some workers residing in migratory farmworker camps (group quarters).

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**Notes:**
The county experiences seasonal labor force patterns due to thee large variety of agricultural activities and substantial packing and shipping operations.

## Strategies for Using ACS Data

- Don't try to analyze all the data all at once.
- Compare with administrative records or census data.
- Don't assume the census picture is more accurate.
- Check the quality measures.
- Consider whether the data make sense.
- Use and provide standard errors.
- Communicate with the Census Bureau.

**Notes:**
There are differences between the Census and the ACS, some statistically significant differences.  These may ultimately be welcome differences if the ACS data are consistent, more current and of higher quality than data from the decennial census long-form sample.  A few suggestions as you proceed to use the ACS data:
 As you do your own analysis, don't try to analyze all the data all at once even if you use all the items or must supply them to others.
 Concentrate on the data items that you already use in your work or frequently.  Compare those items with the census data.
 Don't assume the census picture is more accurate.  Check the quality measures.
 Compare ACS and census data to administrative records that you may have available.
 Consider whether the data make sense.
 Learn to use and provide standard errors supplied with ACS data.

Communicate your findings with the Census Bureau and others evaluating the ACS data.  This will improve the survey as it matures. 

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## Continuing ACS Issues

- Collect and incorporate group quarters population data.
- Improve the Bureau's intercensal population and housing estimates used as ACS controls.
- Maintain sufficient sample size.
- Assist data users to use averaged data and confidence intervals.

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## Bureau Assistance for ACS Data Users

**ACS Data Users Guide**
- Scheduled for September 30, 2005 release
**ACS Technical Paper**
- Scheduled for September 30, 2005 release
**Data User Workshops**
- September 14, 2005 SDC & FSCPE Training
- LiveMeeting training available
- contact Customer Liaison Office
- Other workshops to be announced
**Contact us: cmo.acs@census.gov**

## Contact Information

- Linda Gage
- _[Linda.Gage@](mailto:Linda.Gage@dof.ca.gov)__[dof](mailto:Linda.Gage@dof.ca.gov)__[.ca.](mailto:Linda.Gage@dof.ca.gov)__[gov](mailto:Linda.Gage@dof.ca.gov)_
- (916) 323-4086
- _[http://www.dof.ca.gov/](http://www.dof.ca.gov/)_
- 	Select “Demographic Information”

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