We investigate the distribution of mass M and orbital period P of extra-solar planets , taking account of selection effects due to the limited velocity precision and duration of existing surveys .
We fit the data on 63 planets to a power-law distribution of the form dn = CM ^ { - \alpha } P ^ { - \beta } ( dM / M ) ( dP / P ) , and find \alpha = 0.12 \pm 0.10 , \beta = -0.26 \pm 0.06 for M \lesssim 10 M _ { \mathrm { J } } , where M _ { \mathrm { J } } is the Jupiter mass .
The correlation coefficient between these two exponents is -0.32 , indicating that uncertainties in the two distributions are coupled .
We estimate that 3 % of solar-type stars have companions in the range 1 M _ { \mathrm { J } } < M < 10 M _ { \mathrm { J } } , 2 \hbox { d } < P < 10 \hbox { yr } .