1. 1 Disclosure control and small area statistics Vilni Verner Holst Bloch Cand.scient. landscape ecology and natural resources Statistics Norway Otervegen 23 N - 2225 Kongsvinger Tel : ++47 / 62 88 50 62 Fax : ++47 / 62 88 54 59 E-mail : vvh@ssb.no Grids or blobs? With comparison of two small areas

2. 2 Increasing demand for disclosure control Even smaller area statistics - easier to identify/recognice persons or communities More detailed statistics – more sensitive data More available statistics – easier to combine and derive other information (classic ex.: elder single person with lots of money)

3. 3 Persons Addresses Disclosure depend on geography Oslo municipality – 66 000 addresses (coordinate pairs) (radius 75 m)

4. 4 Disclosure depend on topic

5. 5 Disclosure varies with time and society Norwegian population cencus 1910 - about amongst others; returned norwegian-americans, dissidents, blind people, deaf people and lunitics

6. 6 Stable land units makes measuring change in geographical concentration easier (?) Measuring co-variation when lacking exact geographical match Easy data handling – do not need GIS Advantages of grid

7. 7 Advantages of blobs High geographical accuracy Easy to read – less ”noise” in the map

8. 8 A comparison Central Oslo Stovner

9. 9 Central Oslo Stovner Information on address level

10. 10 Residents per 100 x 100 m gridcell Central Oslo Stovner

11. 11 Employees per 100 x 100 m gridcell Central Oslo Stovner

12. 12 Education in neighbourhood Central Oslo Stovner

13. 13 Disclosure rules in Statistics Norway Blobs Grids Statistics based on this method – given criterias of radius minimum 75 m, minimum 10 livingaddreses and 10 units – may be published. Standard criterias for disclosure control yet to be decided. In practice minimum classes has been 1-4 residents or 1-19 employees.