If there was a 25% requirement the banks participation would be recorded as an Asset on the Balance Sheet. If one is to believe WMI/WMB was truthful in listing their retained interests within their audited filings with the SEC, there is no way that is possible.
Why would there be a need to institute a 5% credit risk retention rule (section 941) in the Dodd–Frank Wall Street Reform and Consumer Protection Act of 2010 if it was mandatory for a firm to retain 25% of MBS issuance's.
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