I was surprise to see that the SOR rate (11 August) went negative this morning. I even refresh my screen a couple of times. I believe this may be due to the Fed decision to keep interest rate low till mid 2013.
Generally, for banks who provide home loan that are pegged to Sibor/SOR, they will take the Sibor/SOR of the 1st day of the month where the loan is disbursed. Therefore at this moment, majority of the loan owners are not affected. If SOR stays negative on the 1st day of the month, i believe they will have some arrangement to it – perhaps a minimum SOR rate impose. Just my personal view.