The ARGUS Software of the SDCproject

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The ARGUS Software of the SDCproject

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Title: The ARGUS Software of the SDCproject

1
The ARGUS Software of the SDC-project

Anco Hundepool
Statistics Netherlands
Washington, August 1999

2
Statistical Disclosure Control

the balance between the need for (more and more)
information and
the privacy of the respondents

3
Statistical Disclosure Control

Need for detailed micro data files
electronic publications
computing power of users
Need for more detailed tables
But....!!!

4
Statistical Disclosure Control

Protection of privacy of respondents
persons, enterprises, institutions
Respondents must be able to trust Statistical
Offices!
Risks
Intruders/ hackers
Accidental recognition
Advanced record linkage techniques

5
Statistical Disclosure Control

Produce safe datafiles and tables
Apply data modification techniques
Preserve as much information
Implemented in ARGUS!

6
Framework of developmentof ARGUS

SDC project
partly subsidised by EU (4th Framework)
Co-operation between The Netherlands, Italy
(Spain) and UK

7
General aims of SDC project

Methodological research in SDC
microdata, tables
concerning statistics, OR
geographical data
(general) SDC Software development
microdata (m-ARGUS)
tables (t-ARGUS)

8
SDC project members

Netherlands
CBS (ARGUS)
TU-Eindhoven (OR for microdata)
Italy
Istat (with Univ. of Rome)(Research/testing)
CPR-Padova (with Univ. Tenerife)(OR for tabular
data)

9
SDC project members

UK
ONS (data)
Univ. Manchester (with Univ. of
Southampton)(Research on SARs)
Univ. Of Leeds (Geographical data)

10
Main software developed in SDC-project

m-ARGUS (CBS and TUE)
micro data
t-ARGUS (CBS and CPR)
tabular data

11
Ideas of m-ARGUS

Intruder uses information of identifying
variables (e.g. region, sex, age, education,
occupation) to identify records.
This leads to the sensitive information

12
m-ARGUS

Levels of protection
public use files (PUF)
micro files for researchers (MUC)universities,
contract etc.
safe-setting

13
Ideas of m-ARGUS

a list of combinations of identifying variables
must checked
find value combinations that are unsafe
e.g. a x b x c
threshold depends on level of protection
Public use files
Micro data for researchers (contract)

14
Ideas of m-ARGUS

eliminate the unsafe combinations
by global recoding (age - agegroup, region
- province)
local suppression (imputing missings)
interactively/automatically
with minimum information loss (entropy)

15
m-ARGUS

For microdata
Developed in Borland C
Windows-95/98
Version 3.0 last SDC-version
interactive/automatic global recoding
automatic local suppression

16
Features of m-ARGUS

can handle large microdata files
only tables derived from microdata are being
used
flexible global recoding
options for automatic mix of global recoding and
local suppression (TU Eindhoven)

17
Addit. features of m-ARGUS

Micro-aggregation
Top/Bottom coding
Rounding

18
m-ARGUS
metadata
microdata
Generate tables
Recoding schemes
Global recoding
Local suppression
Micro aggregation
Top/bottom coding
Rounding
Report
metadata
microdata
19
m-ARGUS input data

Data Fixed format ASCII
Metadata
Name
Position
Missing values (2)
Identification level
Hierarchical coding
Codelist (opt.)

20
Using m-ARGUS

reading data file
generating tables
apply global recodes
local suppression
generate safe file
generate report

21
t-ARGUS
22
Ideas of t-ARGUS

identification of sensitive cellsusing e.g.
dominance rule
at least n (e.g. 2) contributors to a cell
sum of largest 3 contributors 75(one large
contributor could recalculate the contribution of
its competitor)
easy part

23
Ideas of t-ARGUS

Eliminate/protect sensitive cells(hard part)
by applying SDC techniques
table redesign
cell suppression
rounding
interactively and/or automatically
with minimum information loss (e.g. cell weights)

24
Ideas of t-ARGUS

cell suppression in tables with marginals
identify primary sensitive cells
protect primary cells by suppressing additional
(secondary) cells to prevent recalculation (to
some approximation)
with minimal information loss (CPR)

25
t-ARGUS

3-D tables
interactive table redesign
primary secondary cell suppression
optimisation routines for automatic cell
suppression
rounding

26
t-ARGUS
metadata
microdata
tabulation
codelists
redesign
rounding
suppression
report
Safe table
27
Features of t-ARGUS

Initial run through microdata
Determine also top k per cell -sensitive cells
Table redesign possible without going back to
microdata
Uses procedures for secondary cell suppression
using state-of-the optimisation algorithms (CPR)
Prepared for linked tables

28
t-ARGUS