 The forerunner of RATS was a FORTRAN program called SPECTRE, written by economist Christopher A. Sims.SPECTRE was designed to overcome some limitations of existing software that affected Sims' research in the 1970s, by providing spectral analysis and also the ability to run long unrestricted distributed lags.The program was then expanded by Tom Doan, then of the Federal Reserve Bank of Minneapolis, who added ARIMA and VAR capabilities and went on to found the consulting firm that owns and distributes RATS software.