Using microlensing measurements from a sample of 27 image-pairs of 19 lensed quasars we determine a maximum likelihood estimate for the accretion disk size of an average quasar of r _ { s } = 4.0 ^ { +2.4 } _ { -3.1 } light days at rest frame { \langle } \lambda { \rangle } = 1736 Å for microlenses with a mean mass of { \langle } M { \rangle } = 0.3 M _ { \odot } .
This value , in good agreement with previous results from smaller samples , is roughly a factor of 5 greater than the predictions of the standard thin disk model .
The individual size estimates for the 19 quasars in our sample are also in excellent agreement with the results of the joint maximum likelihood analysis .