¹⁴Let us assume that $ct = ct-1 +εt$ and $* ct = ct +υt$ , where $ct$ is real consumption, $* ct$ is the measured consumption, and $υ t$ is the measurement error. Although real consumption growth follows a random walk, the measured consumption growth, $Δc*t =εt- (υt- υt-1)$ , is correlated with the once-lagged information.