  The high rate of planet detection among solar-type stars argues that planet
formation is common. It is also generally assumed that planets form in
protoplanetary discs like those observed in nearby star forming regions. On
what timescale does the transformation from discs to planets occur? Here we
show that current inventories of planets and protoplanetary discs are sensitive
enough to place basic constraints on the timescale and efficiency of the planet
formation process. A comparison of planet detection statistics and the measured
solid reservoirs in T Tauri discs suggests that planet formation is likely
already underway at the few Myr age of the discs in Taurus-Auriga, with a large
fraction of solids having been converted into large objects with low millimeter
opacity and/or sequestered at small disc radii where they are difficult to
detect at millimeter wavelengths.
