Methods and apparatus to perform identity matching across audience measurement systems

A method to perform identity matching, the method comprising:

• building, by executing an instruction with a processor, a data structure based on normalized audience measurement events corresponding to a first audience measurement system, the data structure including a plurality of search spaces;
• identifying, by executing an instruction with the processor, a search space in the data structure based on a query event corresponding to a second audience measurement system;
• determining, by executing an instruction with the processor, the query event and a first audience measurement event in the search space are a candidate match when a distance between the query event and the first audience measurement event satisfies a threshold;
• and
• linking, by executing an instruction with the processor, a first user identifier associated with the first audience measurement system to a second user identifier associated with the second audience measurement system based on a plurality of candidate matches.

A tangible computer readable storage medium comprising instructions that, when executed, cause a machine to at least:

• build a data structure based on normalized audience measurement events corresponding to a first audience measurement system, the data structure including a plurality of search spaces;
• identify a search space in the data structure based on a query event corresponding to a second audience measurement system;
• determine the query event and a first audience measurement event in the search space are a candidate match when a distance between the query event and the first audience measurement event satisfies a threshold;
• and
• link a first user identifier associated with the first audience measurement system to a second user identifier associated with the second audience measurement system based on a plurality of candidate matches.