Moody's downgraded the ratings of Morgan Stanley (MS), Goldman Sachs (GS), JPMorgan Chase (JPM) and Bank of New York Mellon (BK) Thursday.

The agency lowered each of the company's ratings by one notch. It based the move on updated views on the likelihood of government bailouts as well as individual bank considerations, according to a Thursday press release. The downgrades affected more than one type of debt for each company.

The ratings of Bank of America (BAC), Citigroup (NYSE: C), State Street (STT) and Wells Fargo (WFC) remained the same.

The rating outlooks for all eight companies are stable going forward, according to the release, reflecting progress in U.S. bank resolution tools as a result of the Dodd-Frank Act.

"We believe that U.S. bank regulators have made substantive progress in establishing a credible framework to resolve a large, failing bank," Managing Director Robert Young said in the release. "Rather than relying on public funds to bail-out one of these institutions, we expect that bank holding company creditors will be bailed-in and thereby shoulder much of the burden to help recapitalize a failing bank."

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