(Adds full year data, poll of analysts)
BUENOS AIRES, Jan 22 (Reuters) - Argentina's trade surplus narrowed 31 percent in December from the same month a year earlier to $74 million, the government said on Thursday, vastly undershooting market expectations.
The median forecast in a Reuters poll of seven analysts was for a surplus of $300 million.
President Cristina Fernandez's government relies on the surplus to boost dollar supplies on the tightly controlled currency market.
For full year 2014 the government said the trade surplus was $6.69 billion, down from a surplus of $8.01 billion in 2013.
Reporting By Sarah Marsh and Eliana Raszewski; Editing by Diane Craft