Table 2.

Changes in probability of re-identification of anonymised data in BORN (Ontario birth registry dataset) for different levels of generalisation of quasi-identifiers

Scenario	Mother’s date of birth or age	Baby’s date of birth	Mother’s postal code	Baby’s sex	Probability of re‑identification*
S1	Year	day, month, year	3 character	Unchanged	0.973
S2	Year	month, year	3 character	Unchanged	0.677
S3	Age in 5-year groups	month, year	3 character	Unchanged	0.327
S4	Age ≤19, 20-30, 30-40, >40	month, year	3 character	Unchanged	0.23
S5	Age ≤19, 20-30, 30-40, >40	month, year	1 character	Unchanged	0.007
S6	Year	month, year	1 character	Unchanged	0.034
S7	Age in 5-year groups	quarter, year	3 character	Unchanged	0.152
S8	Age ≤19, 20-30, 30-40, >40	quarter, year	3 character	Unchanged	0.1

*Probability was measured using the average re-identification risk metric defined elsewhere.⁷