NEW YORK ( TheStreet) -- On Monday, the yield on 10-year Spanish Bonds rose to 7.5%, the highest level seen since the euro was created in 1999 as Spain's recession deepened. In addition, the Spanish economy contracted 0.4% in the second quarter and is expected to continue contracting going into 2013, according to the Bank of Spain. Global stock prices dropped on Monday as worries increased that Spain -- the fourth largest economy in the euro zone -- might follow Greece in needing a government bailout. Due to these falling stock prices, Spain and Italy issued a 3-month ban on stock short-selling. Separately, regulators will meet over the August holiday in an effort to create a centralized, regime for regulating the European banking sector, according to the Telegraph. United States prosecutors and European regulators are almost ready to start arresting traders involved with manipulating interest rates through Libor, according to a Reuters report. Financial regulators believe future arrests are inevitable and currently are looking through emails to figure out how traders may have worked together to change Libor. Banks such as Citigroup ( C), Barclays and UBS have been implicated in the probe. Increasing concerns surrounding the Libor scandal, documents released by the Federal Reserve show that regulators in the United States and England knew that bankers were "submitting misleading Libor bids during the 2008 financial crisis to make their financial institutions appear stronger than they really were." Included in the Fed documents was a transcript of an April 2008 telephone call in which a Barclays trader told Fed official Fabiola Ravazzolo, "so, we know that we're not posting um, an honest Libor." Some of the largest U.S. banks have created large and complex legal structures as bank holding companies in order to avoid regulation oversight and significant U.S. tax hit, according to a study released by the Federal Reserve Monday. The four "most complex firms" - including JPMorgan Chase ( C), Morgan Stanley ( C), Bank of America ( C) and Goldman Sachs ( C) -- have created more than 2,000 subsidiaries, and two have more than 3,000 subsidiaries, according to the Fed study. Only one bank holding company exceeded 500 subsidiaries prior to the repeal of the Glass-Steagall Act. "The size, scope, and complexity of large U.S. bank holding companies have grown significantly in recent decades, shaped by consolidation, legislative changes, and growth in the overall size of the financial system," the study notes.