We use identification robust tests to show that difference (Dif), level (Lev), and nonlinear (NL) moment conditions, as proposed by Arellano Bond (1991, Review of Economic Studies 58, 277–297), Ahn Schmidt (1995, Journal Econometrics 68, 5–27), Bover 29–51), Blundell (1998, 87, 115–143) for the linear dynamic panel data model, do not separately identify autoregressive parameter when its true va...