Big data analytics has been slowly adopted in the public sector. In particular, there is potential to use social media as a data source of big data analytics, whereas previous use cases in the policy cycle mainly focused on communication. This paper sheds light on the economic prediction as one of influential policy field and discuss opportunities and challenges if governments use social media in the economic prediction. Two cases of economic prediction with/without social media are selected to compare those points: the UK government, and the Japanese government. This paper identifies three opportunities; governments can (1) achieve a national-level economic indicator; (2) intervene economy in timely and flexibly manner; and (3) become a centre of excellence to develop such models. On the other hand, there are also three challenges; governments need to (1) develop more sophisticated models; (2) explain the outcome clearly; and (3) consider some ethical issues. This paper concludes with some advice to practitioners in the implementation phase.