“OnTheMap” The Census Bureau’s New Tool for Residence-Workplace Analysis Fredrik Andersson and Jeremy Wu May 7, 2007 Daytona Beach, FL

Overview of Presentation 1.Live demo of OnTheMap (Jeremy) 2.The Disclosure Avoidance Protocol for OnTheMap (Fredrik) 3.Analytical validity and confidentiality protection (Fredrik) 4.Data Access (Fredrik)

1.Demonstration of OnTheMap

(Local Employment Dynamics)

On The Map v.1 LEHD’s online dynamic mapping tool 17 states online Completed 12/06 Where do workers live? Where do people work? Companion reports on age, earnings, and industry First partial synthetic data product User select areas Block is base unit for display; block group is base unit for report Modular geographic layers such as community colleges and zip codes

Optional Layers

Where are Workers Residing in Sausalito, CA Employed?

Concentric Circle Report

On The Map Version 2 Up to 44 LED partner states Add 2004 data to data Cross-state patterns for all states Enhanced multi-year reports Additional geographies Will become available in phases between April and September 2007

2. The Disclosure Avoidance Protocol for OnTheMap

The Challenge: Maximize Analytical Validity of Data Subject to Strict Confidentiality Protection Constraints Analytical Validity of Data Degree of confidentiality protection Synthetic Data Cell Suppressio n

Basic Facts about the Disclosure Protection System for OnTheMap Goal: “to protect confidentiality while preserving analytical validity of data” –No cell suppression –Synthetic place of residence data –Workplace data protected by QWI disclosure protection system (“dynamically consistent noise infusion”) First-ever data product released by a Statistical Agency (Feb 2006) that relies on synthetic data method as its primary disclosure avoidance technique

Disclosure Avoidance Bayesian statistical techniques to create a partially synthetic version of the confidential data –Block of origin counts sampled from a posterior predictive distribution conditional on destination block and worker characteristics (earnings, industry, age, ownership sector) –The posterior predictive distribution is derived from combining the likelihood (“true data”) with a prior So, what does this really mean???

Creation of Synthetic Data Fictional example: Distribution of place of residence for workers in a specific block, industry, earnings category, age category, ownership sector Q: Why not sample directly from the likelihood/What’s the role of a prior? Q: How are the priors constructed? Q: How much weight is given to the prior?

Key Implication The relative weight of the prior when sampling from the posterior distribution is inversely related to the size of the population being synthesized –For larger populations the synthetic place of residence data closely mimic underlying data –For small populations the synthetic place of residence data are relatively more “noisy” to protect confidentiality Important to keep in mind when making inferences using OnTheMap How “noisy” an estimate is can be assessed by taking advantage of all 10 implicates of the synthetic data available on the virtual RDC

3. Analytical Validity & Confidentiality Protection

The residence patterns in synthetic data mimic confidential data well

Level of protection increases as population in work block decreases

Key Properties in data, such as commute distance, are preserved in synthetic data

4. Data Access

OnTheMap Data (public use data) Origin-Destination (OD) matrix Residence Area Characteristics Workplace Area Characteristics Quarterly Workforce Indicators (QWI) (below not distributed) TIGER files Geographic shape files, etc.

OnTheMap Data There are 10 implicates; only the first is used in OnTheMap at this time OnTheMap v2 for 17 states to be released May 31 – these and future data to be made available within 6 weeks of release OnTheMap v1 data will be withdrawn in June

Cornell CISER Site No project approval needed to register Read documentation and descriptions Very limited support Not affiliated with the Census Bureau

Getting Your Feedback Join the OnTheMap listserv: Or send an with Yes in the subject line to

Contact Us Program Manager General Comments/Suggestions Website (Local Employment Dynamics)