Andrew Kalotay Associates will have exclusive rights to its new mortgage-backed securities valuation model. Coupled Lattice Efficiency Analysis (CLEAN), which determines refinancings based on mortgagor credit and then discounts the resulting cash flows using an MBS issuer's credit, has been approved to be patented. The new model's methodology is described as an "option-theoretic approach" to MBS valuation. CLEAN is able to track mortgagors with a higher propensity to refinance, says Andrew Kalotay and Assoc., automatically capturing refinance fatigue following periods of low interest rates. And the model's option-based method ensures consistency with the valuation of callable agency debt. The founding firm says the approach allows for speedy processing -- 14,000 securities per minute --  without compromising accuracy. The model is a major breakthrough, says Andrew Kalotay, the firm's founder. "It's truly market-implied," he says. Write to Kelly Curran.