WASHINGTON (AFP) - The US economy remains in recession, despite positive signs of growth, because the data are too preliminary to be reliable, the official US arbiter of business cycles said Monday. The National Bureau of Economic Research (NBER) said its business cycle-dating committee met Thursday to review the most recent data for all indicators relevant to deciding whether there was an end to the recession that began in December 2007. Although most indicators have turned up, the committee decided that the determination of the trough date on the basis of current data would be premature, the NBER, based in Cambridge, Massachusetts, said in a statement. Many indicators are quite preliminary at this time and will be revised in coming months, it said. The private, nonpartisan NBER, which groups many of the leading US economists, determines the month when recessions begin and end. The dates are regularly used as references by economists and authorities. The NBER does not use the common definition of recession as two consecutive quarters of contraction of gross domestic product, a broad measure of goods and services output. Rather, the research organization makes its determination on GDP and factors including employment levels, industrial production cycles and household incomes. It took the NBER a year to determine that the recession began in December 2007, and on Thursday the committee confirmed that date following a review of data. Most economists believe the economy turned the corner to expansion between June and August of 2009, which would make the recession the longest since the Great Depression that started in August 1929 and ended in March 1933.