Table 1.

Count of distinct values and selectivity of each identifier field within the set of 7,293 linked records.

Identifier Field	Distinct Values in the Physician Billing Record Set	Selectivity in the Physician Billing Record Set	Distinct Values in the Newborn Medical Record Set	Selectivity in the Newborn Medical Record Set
Infant Sex	2	0.0%	2	0.0%
Zip Code	270	3.7%	277	3.8%
Birth Weight (Nearest 10 Grams)	430	5.9%	429	5.9%
Mother First Name (Soundex-Encoded)	1,022	14.0%	902	12.4%
Date of Birth	1,092	15.0%	1092	15.0%
Infant First Name (Soundex-Encoded)	1,103	15.1%	889	12.2%
Father Surname (Soundex-Encoded)*	1,494	20.5%	0	0.0%
Street Name (Soundex-Encoded)	1,765	24.2%	1,730	23.7%
Birth Weight (Exact)	2,089	28.6%	1,709	23.4%
Mother Surname (Soundex-Encoded)	2,367	32.5%	2,408	33.0%
Father Surname*	2,380	32.6%	0	0.0%
Infant Surname (Soundex-Encoded)	2,429	33.3%	2,471	33.9%
Street Name	2,653	36.4%	2,533	34.7%
Mother First Name	3,120	42.8%	2,808	38.5%
Infant First Name	3,164	43.4%	2,305	31.6%
Mother Surname	3,828	52.5%	3,834	52.6%
Street Number	3,950	54.1%	3,912	53.6%
Infant Surname	3,956	54.2%	3,977	54.5%
Street Address	6,976	95.7%	6,687	91.7%

^*Father’s surname was not available in the newborn medical record.