include changes in demand arising from Christmas, Easter or other public holidays. Normal, expected changes in weather are not included. The net balance of companies reporting an improvement in a variable less those reporting a deterioration is then adjusted to allow for the percentages of companies reporting seasonal induced increases or decreases in the variable. Other PMI surveys Similar purchasing managers indices are published by the Ifo Institute for Economic Research in Germany, the Bank of Japan in Japan (Tankan), the Caixin China PMI published by Markit and the Swedish PMI run by private bank Swedbank. The Singapore PMI (新加坡采购经理指数) is published by Singapore Institute of Purchasing and Materials Management on a monthly basis. It was developed by Professor Philip Poh. He has also contributed to the development of the Chinese PMI, and the Euro PMI. The PRIX index uses a diffusion index methodology based on that of PMIs. However, rather than drawing on purchasing managers, it uses country analysts based in the world's 20 largest oil exporting countries to forecast political events that may affect global oil exports. The PRIX index is updated quarterly and published for free on the internet. See also Ivey Index References Procurement Business indices Surveys (human research)