IMPROVING CONFIDENTIALITY WITH tau-ARGUS BY FOCUSSING ON

CLEVER USAGE OF MICRODATA

Roland van der Meijden MSc.

± 10 minutes

Content of presentation

• tau-Argus• Tuning possibilities• Hierarchies• Historyfile, information loss and base material• Conclusions

Tau-Argus

Automated cell suppression software

Calculates confidentiality effects on all dimensions of a table simultaneously

Offers 4 confidentiality rules:- (n,k)-rule / dominance rule- p%-rule- p-q-rule / prior-posterior-rule- Minimum frequency rule

Tuning possibilities

Hierarchies: The way hierarchies are built is of influence on how secondary suppressions are applied.

History file: A preference can be given for which cells may or must be secondarily confidential.

Information loss weights: Information will be lost when applying secondary suppressions. The way tau-Argus calculates this information loss can be adjusted.

Base material: The way the microdata and preferred output are composed is of influence on the way secondary suppressions are applied.

Hierarchies (1)

Total Total Small

Large

A

B

C

D

E

0

1

2

3

4

5

6

7

0

1

2

3

4

5

6

7

Small

Large A

B

8

9

8

9

Old ‘narrow’ classification New ‘wide’ classification

Figure 1: A rearrangement of subcategories within a size class classification.

Hierarchies (2)

Status narrow size class

size class total

size class S - L

size class A - E

size class 1 - 9

% cells % cells % cells % cells

A frequency unsafe 32,8 42,0 52,9 61,4D secondary unsafe 27,2 31,5 25,1 17,9V safe 35,1 25,1 21,5 20,4

Status wide size class

size class total

size class S - L

size class A - E

size class 1 - 9

% cells % cells % cells % cells

A frequency unsafe 32,8 41,1 49,3 61,4D secondary unsafe 26,5 31,5 28,4 18,1V safe 35,7 25,8 21,6 20,2

Historyfile, information loss and base material (1)

Historyfile– Confidential, publishable, preferably do (not) suppress secondarily

Information loss– Cell value, frequency, equal and distance

Base material– Small area estimation, deliberately adjusting microdata and coordination of publication obligations

Historyfile, information loss and base material (2)

Methods for determining information loss

Cell value Frequency

Status2nd

digit NACE

3rd digit

NACE

4th digit

NACE

5th digit

NACE

2nd digit

NACE

3rd digit

NACE

4th digit NACE

5th digit

NACE

A frequency unsafe 0 195 2686 7995 0 195 2686 7995

B dominance unsafe 0 26 216 641 0 26 216 641

D secondary unsafe 4 321 2837 6806 4 298 2638 6423

V safe 285 1382 4813 8351 285 1405 5007 8724

Conclusions

- tau-Argus is a tool that is helpful in calculating confidentiality effects.

- The confidentiality pattern can be influenced.

- Improving the confidentiality pattern, takes a lot of effort.

- Both tooling and the way base material is used are of influence on the confidentiality pattern.