We compare red clump stars with parallaxes known to better than 10 % in the Hipparcos catalog and corrected for the interstellar extinction , with the OGLE red clump stars in Baade ’ s Window also corrected for the interstellar extinction .
There are \sim 600 and \sim 10 , 000 such stars in the two data sets , respectively .
We find empirically that the average I-band magnitude of red clump stars does not depend on their intrinsic color in the range 0.8 < ( V - I ) _ { 0 } < 1.4 .
The red clump luminosity function is well represented by a gaussian with the peak at M _ { I _ { 0 } ,m } = -0.26 , and the dispersion \sigma _ { RC } \approx 0.2 mag .
This allows a single step determination of the distance to the galactic center and gives R _ { 0 } = 8.4 \pm 0.4 kpc .
The number of red clump stars is so large that a formal statistical error is only \sim 1 \% .

The local stars are relatively blue and have a small color dispersion : \langle ( V - I ) \rangle = 1.01 , \sigma _ { ( V - I ) } = 0.08 , while for the bulge stars \langle ( V - I ) _ { 0 } \rangle = 1.22 , \sigma _ { ( V - I ) _ { 0 } } = 0.14 .
Presumably , the bulge population has a broader range and a higher average metallicity than the local disk population .