For the United States, in the business sector, the funds from abroad previously included in the business-financed BERD, are available separately from 2009. In the higher education sector, all fields of SSH are included from 2003 onwards.

Following a survey of federally-funded research and development centers (FFRDCs) in 2005, it was concluded that FFRDC R&D belongs in the government sector - rather than the sector of the FFRDC administrator, as had been reported in the past.  R&D expenditures by FFRDCs were reclassified from the other three R&D performing sectors to the Government sector; previously published data were revised accordingly. Between 2003 and 2004, the method used to classify data by industry has been revised. This particularly affects the ISIC category "wholesale trade" and consequently the BERD for total services. 

U.S. R&D data are generally comparable, but there are some areas of underestimation:
i) Up to 2008, Government sector R&D performance covers only federal government activities.  That by State and local government establishments is excluded; 
ii) Except for the Government sector, the R&D data exclude capital expenditures. For the Business Enterprise sector, depreciation is reported in place of gross capital expenditures.

As from reference year 1999, the North American Industrial Classification System (NAICS) was introduced into the survey. The switch from SIC-based estimates to NAICS-based estimates constitutes a break in time series in the detailed industry series.

Breakdown by type of R&D (basic research, applied research, etc.) was revised back to 1998 in the business enterprise and higher education sectors due to improved estimation procedures.  Higher education (and national total) data were also revised due to an improved methodology that corrects for double-counting of R&D funds passed between institutions.