The CFTC's Division of Clearing and Intermediary Oversight regularly receives financial reports from futures commission merchants (FCMs). The data is taken from the most recent financial report received by the Division just before publication. The summary is available in both Adobe PDF and Microsoft Excel spreadsheet formats for viewing or downloading.

Therefore, iff you wish to know the net capital of each reguated brokerages you can find it in Selected Financial Data for Futures Commission Merchants

http://www.cftc.gov/tm/tmfcm.htm