  We introduce a novel framework to model limited lookahead in congestion
games. Intuitively, the players enter the game sequentially and choose an
optimal action under the assumption that the $k-1$ subsequent players play
subgame-perfectly. Our model naturally interpolates between outcomes of greedy
best-response ($k=1$) and subgame-perfect outcomes ($k=n$, the number of
players). We study the impact of limited lookahead (parameterized by $k$) on
the stability and inefficiency of the resulting outcomes. As our results
reveal, increased lookahead does not necessarily lead to better outcomes; in
fact, its effect crucially depends on the existence of ties and the type of
game under consideration.
  More specifically, already for very simple network congestion games we show
that subgame-perfect outcomes (full lookahead) can be unstable, whereas greedy
best-response outcomes (no lookahead) are known to be stable. We show that this
instability is due to player indifferences (ties). If the game is generic (no
ties exist) then all outcomes are stable, independent of the lookahead $k$. In
particular, this implies that the price of anarchy of $k$-lookahead outcomes
(for arbitrary $k$) equals the standard price of anarchy. For special cases of
cost-sharing games and consensus games we show that no lookahead leads to
stable outcomes. Again this can be resolved by removing ties, though for
cost-sharing games only full lookahead provides stable outcomes. We also
identify a class of generic cost-sharing games for which the inefficiency
decreases as the lookahead $k$ increases.
