1. Anco Hundepool Sarah Giessing
ProdCom Rounding
Anco Hundepool
Sarah Giessing

2. Overview Current situation Cell suppression or rounding
ProdCom solution
Prototype
Further work

3. Current situation (MS)
Member states collect and process the data.
MS applies its own conf. rules.
(Dom. rule, freq rule, p% rule)
MS publishes its own data first.
Process done individually by each MS.
Then MS sends the data to Eurostat

4. Current situation (Eurostat)
Eurostat receives MS data plus conf. info.
Problem:
Eurostat cannot publish many EU-aggregates because some countries are blocked.
Eurostat should respect/safeguard the national confidential cells.
Result: many EU-aggregates are blocked.

5. ProdCom conf. chapter If one country is conf.: EU-aggregate is conf,
If 2 countries are conf. and both are singleton: EU-aggregate is blocked.
If 2 countries are conf. and one is a zero-cell then EU-aggregate is blocked
If 2 or more countries are conf. and there is dominance then EU-aggregate is blocked
If all countries are safe, then EU-aggregate is OK

6. ProdCom conf. chapter Result: Many ProdCom aggregates are blocked. 
The usefulness of this publication is ‘limited’ 
Is there a way out?

7. ProdCom rounding project
Cell suppression = replacing the conf. cell value by an interval.
Minimum size of the interval is determined by the sensitivity rule. (distance to a safe cell).
Dom. rule and p% rule give a clear formula.
Freq. rule not but we choose a percentage.

8. ProdCom rounding project
Conclusion:
Eurostat should respect these protection intervals.
Eurostat can publish approximations or intervals of the EU-aggregates.
EU-intervals should respect the MS-intervals.
So build those intervals.

9. t-ARGUS Standard solution: Cell suppression.
Finding a safe pattern and minimising information loss is a hard problem.
Efficient solutions offered by t-ARGUS.
Lead to too many suppression on the EU-level (because suppression of additional member state level cells not allowed)

10. Rounding Rounded value = interval. 37 rounded to 40 base 10 = [35,44]
If interval is large enough the rounded value (= interval) can be published.

11. Simple rounding does not work
Intervals often smaller as rounding base
because of table relations
Sometimes the rounding can be undone
Does not always provide upper protection
even with large rounding base
upper bound may still be sensitive – dominance problem!!!

12. Simple rounding does not work
Intervals often smaller as rounding base
Example:
Cell value 5800, contributions 5200, 300, 300
sensitive at (1,85)-dominance rule
Protection of 400 would be enough (5200 not dominant f.i. in 6200).
Still, simple rounding with base 1000 may not provide sufficient protection:
Assume table relation Becomes after rounding
6400 | |
So upper bound for 5800 is But 5200 is still dominant in 6000 !!!
< 6500
≥ 500
< 6000

13. Simple rounding does not work
Sometimes rounding can be undone
Example
28 |
30 |

14. Simple rounding does not work
Does not always provide upper protection
Example:
Cell value 5400, contributions 4800, 300, 300
sensitive at (1,85)-dominance rule
Protection of 300 would be enough (4800 not dominant f.i. in 5700).
Still, simple rounding with base 1000 does not provide sufficient protection:
Cell value Becomes after rounding
Upper bound 5500 too close: is still dominant in 5500 !!!
< 5500

15. Countrolled Rounding
Controlled rounding preserves additivity and avoids underprotection problems.
In higher dimensions very difficult.
Bounds are twice as large.
In t-ARGUS a rounder solution similar to cell-suppression.
Based on optimisation techniques.
Originally designed for freq. tables but can also be used to protect magnitude data.

16. Rounding Use t-ARGUS rounder to compute EU-aggregates
Which rounding base?
At least larger than largest protection interval.
If not enough iterate till enough

17. Rounding base Two series: Simple (powers of 10)
10,20,…,80, 90,100,200,…,800, 900, 1000, 2000, …, 8000, 9000,
Version 2 less information loss, more difficult to explain.
Both have been implemented.
Your choice.

18. Results (rounding base)
Rounding base (% EU total)
Frequency
Proc Proc 2
0-<1 23 70
1-<5
190
277
5-<10 82
109
10-<20 92 58
20-<50
107 15
50+ 39 4

19. Results (Iterations) Number of iterations Frequency Proc 1 Proc 2 1
448
162 2 84
195 3
111 4 48 5+ 17

20. Rounding Parameters to be chosen: Prot. interval freq. unsafe (%)
Prot. interval secondaries (%)
Prot. interval zero-cells (interval)
In above examples
Freq: 10%, Sec:10%, Zero 100.

21. Prototype Indicate the data file Indicate the rules file
A few parameters
And then all will be done automatically

22. Program

23. Prototype
Output:
File with EU-aggregates Orig. values if safe Rounded values + rounding base if unsafe Comma-separated; easily loaded in Excel
Report/log file

24. Future
A bit more testing
Extend the aggregates

25. Conclusions Solution based on rounding has been created.
Looks satisfactorily for the ProdCom problem
Most EU-aggregates rounded moderately only; a few might still be considered suppressed.
Much more useful ProdCom publication.