Based on the "2010 Methodology Statement: Esri Data�??Business Locations and Business Summary" whitepaper, I believe the "Employees" variable (G01_TotEmp) in the 2010/2015 ESRI Demographic data is an aggregation or "roll-up" by geographies of the "Employee Count" (NUMBER_EMP) field in the InfoGroup business points. Likewise with the Number of Businesses variables.
[INDENT]"Esri uses the geographic codes to report business data for summary areas such as states, counties, census tracts, and block groups. Aggregations by ZIP Codes are created from the business database. ZIP Codes from Infogroup may differ from the residential ZIP Codes in the Esri® demographic databases because Infogroup includes business-only ZIP Codes that are unique to a particular establishment and include no residential area. The coordinates of each business are used to assign it to a user-defined polygon"[/INDENT]
I'm very disappointed that these Business Summary variables were excluded from ESRI's 2011/2016 demographic data. Supposedly they will be included in the 2012/2017 data.