Initial estimate of GDP systematically biased up

The Initial estimate of GDP systematically biased up says Nouriel Roubini in a recent twitter message , "Q1 (Q3) growh initially estimated at 1.5% (2.5) then sharply revised downward to 0.4% (1.8).Initial estimate of GDP systematically biased up" "As we expected Q3 growth estimate down to 1.8% on much lower discretionary service spending. This is a bias in all initial GDP estimates" he added "Upward biases in initial GDP estimates: consumption of discretionary services; sample of large producers & retailers while SME are slumping" he explained