ExxonMobil was the top company in the rankings with a total market capitalization of $406 billion. ExxonMobil was briefly overtaken by Apple in the previous rankings in September, but has subsequently recovered the top position. Sustained high oil prices have supported ExxonMobil's share price relative to other sectors.

The total market capitalization of the top global 500 companies declined by 8.7 percent during 2011, to total $22.9 trillion, compared with $25.1 trillion at the end of 2010. The fall in market capitalization of the world's leading companies was a consequence of the poor performance of global equity markets in 2011 as global share prices fell. The MSCI World index for large companies fell by 7.6 percent in 2011. The decline was mainly a result of the euro zone debt crisis and concerns about fiscal retrenchment in developed markets, the QNB Capital report said.

Banking was the most strongly represented sector in the company rankings. It accounted for 14.1 percent of overall market capitalization and included 67 companies. The banking sector was followed by oil and gas producers with a 13.7 percent share that included 43 companies.

US companies dominate the top global 500 list, with a total of 177 companies accounting for 40.8 percent of overall market capitalization. Japanese companies come in a distant second, with a total of 37 companies accounting for 5.3 percent of the total.

Six companies from the Middle East and North Africa region (MENA) made it into the rankings, accounting for 0.8 percent of the market capitalization of the top 500 companies. The top two MENA companies are both Saudi Arabian. The petrochemicals company, Saudi Basic Industries Corp. (SABIC), ranked 68th with a market capitalization of $76.6 billion and Al-Rajhi Bank, ranked 267th with a market capitalization of $27.7 billion. A third Saudi company, Saudi Telecom, also made it into the top 500 rankings at 452nd with a market capitalization of $18.0 billion.

Of the remaining three MENA companies in the top 500 rankings, two were Qatari, QNB Group and Industries Qatar (IQ), accounting for 0.2 percent of the total top 500 market capitalization. QNB Group came in at 278th place with a market capitalization of US$26.6bn, up from $19.9 billion at the end of 2010.

During 2011, QNB Group's market capitalization has been boosted by a 6.8 percent increase in its share price and a rights issue for 25 percent of the group's shares. The strong performance of QNB Group's share price was driven by rising profitability and strong growth of total assets. Net income at the bank has risen by 32 percent in 2011 to $2.1 billion and total assets rose by 35 percent to $82.9 billion.

QNB Group has made rapid progress up the rankings from 500th in March 2011 to 278th in December 2011. According to QNB Capital, falling global equity markets have led to a drop in the market capitalization of most of the companies in the top 500 rankings. The increase in QNB's share price has therefore led to a significant improvement in its rank by market capitalization.

Industries Qatar has also moved up the rankings from 461st at the end of 2010 to 384th in December 2011. Over this period IQ's share price increased by 15.5 percent. IQ's strong performance was a consequence of strong profits, which rose to $1.7 billion in the third quarter of 2011, a 35.0 percent increase over the same period in 2010. IQ's profit growth was driven by a recovery in the petrochemicals sector, which has benefited from recent sustained high oil prices.

The strong performance of QNB Group and IQ in 2011 in terms of their share price and market capitalization has been a consequence of their ability to benefit from the strength of the Qatari economy relative to the advanced economies that dominate the FT's top global 500 rankings, according to QNB Capital. QNB Capital estimates that real GDP growth in Qatar was 21.0 percent in 2011 compared with the IMF's estimate for growth in advanced economies of 1.6 percent.

In Qatar, strong growth and high prices in the hydrocarbons sector have supported growth in non-hydrocarbons sectors, presenting Qatari companies with good opportunities for growth.