We have seen this phenomenon pressed upon us repeatedly and often tragically. One result of our information gaps is that national problems go nearly unnoticed until they are forced upon us by some significant and shocking event. Suddenly. we learn of widespread hunger in America. of the rapid deterioration of our environment. of dangerous tensions and unrest in our great urban centers. of the shocking conditions under which migrant farmworkers live. and of the absence of decent medical care for tens of millions of our citizens. We desperately need ways to monitor such problems before they destroy or seriously damage our society. Another tremendously expensive consequence of our lack of adequate information is that we devise and operate programs based on myth and ignorance or guess and supposition.