The world's most populous nation,I.35 billion strong,will soon have too few people-or,rather,too few of the right kind of people. More than three decades of government-mandated family planning,often called the one-child policy,have succeeded beyond the architect's most grandiose dreams. Add to that the natural inclination of richer, more educated people like Liu and his wife to limit their family size,and China's population growth is projected to taper off within I5 years.