Clap is an information system that is fed from various sources.
1. The statistical directory required for the compilation of business statistics (SIRUS).
2. Data on salaried employment is produced by aligning information from four sources:
- annual Declarations of social data (DADS) ;
- summary contributions forms  from URSSAF (Organisation for the payment of social security and family benefit contributions) which make up the "Epure" information system;
- the information system on civil servants;
- data from the agricultural mutual benefit social fund (MSA) which complements URSSAF data for sectors of activity associated with agriculture (starting with data for the 2007 financial year).
Data on pay that appears in Clap are the total sum of gross wages for employees in an establishment. Pay corresponds to employee salaries and bonuses in the course of the financial year.
The classification used for the data in Clap until the 2007 financial year is the NAF rev.1.
After the 2008 year of reference, the aggregation levels associated specifically with NAF rev. 2 will be used. The Clap information source is used for economic analysis according to workplace location.
Clap is by no means a substitute for the employment estimates that are produced by INSEE; CLAP assesses employment according to job numbers, while INSEE's estimates assess employment according to the number of people occupied at the workplace.