  An intuitive outer bound for the multiterminal source coding problem is
given. The proposed bound explicitly couples the rate distortion functions for
each source and correlation measures which derive from a "strong" data
processing inequality. Unlike many standard outer bounds, the proposed bound is
not parameterized by a continuous family of auxiliary random variables, but
instead only requires maximizing two ratios of divergences which do not depend
on the distortion functions under consideration.
