Promixities computed according to the methodology presented by
C. A. Hidalgo, B. Klinger, A.-L. Barabasi, R. Haussman in
"The Product Space Conditions the Development of Nations", Science, vol. 317, 27 July 2007.
The supplementary online materials are free:
http://www.nd.edu/~networks/productspace/Resources/SupplementaryMaterialProductSpace.doc

As for the data, source: http://cid.econ.ucdavis.edu/data/undata/undata.html

Constructed from United Nations trade data by Robert Feenstra and Robert Lipsey, under a grant from the National Science Foundation to the NBER.
Sum of 1998, 1999, and 2000 data: Economics Web Institute.

Values in thousands of dollars, current prices.

The correspondence between product category name and SITC code is given in a separate TXT file.
To obtain the world market of a certain product, look first at SITC_Rev_3_english_structure.txt, searching for the product you are interested in, get its SITC code (at 4-digits level), then filter the DBF dataset.


For further information, see http://cid.econ.ucdavis.edu/data/undata/NBER-UN_Data_Documentation_w11040.pdf for further information.