In one sign of the buoyant start-up market, venture capitalists are seeing more interest from “secondary” investors.

Sometimes, a venture firm makes an investment in a company, and decides to turn around and sell the ownership position to another player. For example, Ron Conway, a prominent angel investor, did that several years ago, when he sold some of his interests to Credit Suisse First Boston. CSFB, in this situation, is called a “secondary” investor.

Pricing levels in the secondary market reached new heights last year, and will likely strengthen further in the next year or two, according to a study by secondary adviser Cogent Partners cited by VentureWire today (sub required):

The study found that the average high bid for secondaries was 108% of net asset value, or NAV, up from 94.2% in its 2005 study and the first time this figure has exceeded book value for the full year. While the average high bid for buyouts remained at basically the same level as last year, 108.9%, venture secondaries saw a big increase, to 108.2% from 83.5%…

Several factors were driving the change, Cogent said:

For one, venture portfolios are being valued more realistically than they were in the period immediately after the bubble, as companies have either disappeared or raised another round at more realistic valuations. At the same time, the venture funds now for sale are more mature than they were two or three years ago, meaning their true value is easier to estimate. In addition, this particular sample includes a number of brand name general partners, for which demand is generally high…