why lagged data as instrument why use lagged dv for regression why use lagged dv? why use lagged dv as instrument why use a lagged dv as instrument why does stata use dv as instrument why use dv as instrument why is dv used as instrument why use lagged dv as instrument why use a lagged dv as an instrument what is lagged variable why use lagged dv data which variable is an instrumental variable? why use iv as instrument what is the function of the iv v variable in stata why use lagged dv as instruments? why use a lagged dv as an instrumental variable what is instrumental variable why use a lagged dv as instrument why use instrumental variable as instrument