I think this is an unfair statement, because it's easier to find gas planets. From the article I posted today:
The techniques currently used to find exoplanets were strongly biased towards detecting gas giant planets orbiting at short distances from their parent stars.
The OGLE planets were found using a technique called gravitational micro-lensing, in which light from the faraway planets is bent and magnified by the gravity of a foreground object, in this case a another star.