LACK OF DATA

Finally, there are securities for which pricing history is completely unavailable. Real estate, asset-backed securities, private equity investments, and complex derivatives are all types of investments for which meaningful market data is effectively unavailable.

In these situations, the general approach is to find a similar, “proxy” security or portfolio of securities that match the payoff structure and risk of the position in question. Emanuel Derman, in his book My Life as a Quant: Reflections on Physics and Finance, wrote, “I believe that you can summarize the essence of quantitative finance on one leg. . . . If you want to know the value of a security, use the price of another security that's as similar to it as possible. All the rest is modeling. Go and build.”