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The world's biggest banks have posted their lowest revenues since 2006, according to industry monitor Coalition.

First-half revenues slumped 11% at 12 of the biggest banks in Europe and the US.

Equities have been hit especially hard, as slow growth and low-interest rates hit Wall Street's biggest names.

Headcount at the world's largest investment banks dropped by 1,500 from January to June.

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Plagued by geopolitical tensions, low interest rates, and slow growth, the world's biggest banks have seen revenues plunge to their lowest levels since 2006.

Sales at 12 of the largest investment banks in Europe and the US dropped 11% to $76.8 billion in the first half of this year — the lowest figure since before the financial crisis, according to data from industry monitor Coalition.

The banks' fixed income, currencies, and commodities (FICC) divisions declined, as did their investment banking (IBD) arms, Coalition said. However, their equities businesses suffered the most with a 17% decline.

Equities may have further to fall, according to the Financial Times, as stricter investor protection regulations in Europe could mean other banking giants join Deutsche Bank in leaving equities to Wall Street's biggest players.

Earnings from Deutsche Bank, Morgan Stanley, and others have missed the mark in recent months.

Deutsche Bank posted a $3.5 billion loss in the second quarter, much wider than the $2.8 billion predicted by Credit Suisse. Morgan Stanley also suffered, with equities-trading revenue down 14% — the worst of any Wall Street Bank — and overall sales-and-trading revenue down 12%.

Headcount in the investment banks also shrunk by 1,500 between January and June, Coalition reported. Both economic uncertainty and technological change played a role in the job cuts, it said.

See More: Headcount at the world's largest investment banks shrank by 1,500 in the first half of 2019, and equities trading took the brunt of it.

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