More recent working papers (and a few older papers) are downloadable from this page.
The links below lead to lists of all working papers published by Impact Project (and later CoPS) since 1975. Most of the older papers are downloadable as scanned PDFs. Originally, the Impact Project hosted 4 models: MACRO (a conventional macro model), BACHUROO (a demographic model), ORANI (a CGE model with short-run focus), and SNAPSHOT (a CGE model solved by linear programming, with a long-run focus). The classification system for working papers still reflects this history:
MACRO Model: MP, M
BACHUROO Model: BP, B
ORANI Model: OP, O
SNAPSHOT Model: SP, S
Computing Documents: C
IMPACT/COPS: IP, I
General Papers A G-01 to G-100 (1976-1993)
General Papers B G-101 to G-200 (1993-2010)
General Papers C G-201 to G-300 (2010-)
Note: P in series number (e.g., BP, OP) signifies preliminary
CAVEAT: Some of the "scanned PDFs" which you can download have been produced by scanning folded A5 booklets which have been dissembled for scanning. The pages may appear to be rotated and shuffled. In such cases, to read the PDF effectively, you need to PRINT IT OUT and re-assemble the pages to create your own folded A5 booklet.