Part of the art of policy-making is developing a sense of how to distinguish noise and signal from this mass of 'information'. Before placing too much weight on an indicator, some knowledge of how it is put together is obviously important.
To this end, it is often worthwhile for people in the policy analysis process to develop a good dialogue with the compilers of these data. On occasion, well-trained people in the bureaucracy have been able to suggest methodological improvements to privately-compiled surveys.