What does political bias and social construction mean?

Could someone explain " to what extent are official statistics open to political bias and social construction?" briefly to me?|||In the 1980s in Britain most people realised that there were around ten million people that had lost there jobs and were either unemployed or were surviving in the black economy. However, to keep official unemployment figures down to what appeared to be a reasonable level the unemployment figures were 'massaged' no less than 17 times giving an acceptable (to the government) figure of four million. That is only one example of how OFFICIAL statistics are open to political bias and social construction.