# A possible typo in Herbst and Schorfheide book of DSGE estimation

In a state-space representation, the measurement equation is something of this form $O_t=H_t s_t + u_t$, where $O_t$ are the observational data at time $t$, $H_t$ is a possibly time-dependent matrix relating the state $s_t$ and the observational data. We can see $u_t$ as the measurement errors at time $t$.

However, in Herbst and Schorfheide book (Bayesian estimation of DSGE models),

we have $s_t$ dependent on $y_{t}$, but not $y_{t-1}$, while the measurement equations are of the form:

Is this a typo? Should I add the $y_{t-1}$ term to $s_t$?