Oslo is one of the most expensive cities in the world. , it is ranked tenth according to the Worldwide Cost of Living Survey provided by Mercer Human Resource Consulting and first according to the Economist Intelligence Unit (EIU). The reason for this discrepancy is that the EIU omits certain factors from its final index calculation, most notably housing. In the 2015 update of the EIU's Worldwide Cost of Living survey, Oslo now ranks as the third most expensive city in the world. Although Oslo does have the most expensive housing market in Norway, it is comparably cheaper than other cities on the list in that regard. Meanwhile, prices on goods and services remain some of the highest of any city. Oslo hosts 2654 of the largest companies in Norway. Within the ranking of Europe's largest cities ordered by their number of companies Oslo is in fifth position. A whole group of oil and gas companies is situated in Oslo.