Impact analyses are considered difficult to use because they tend to be medium and long term endeavours. Criteria to evaluate the effectiveness of spatial planning are mostly sectoral, at least when it comes to short-term evaluations (e.g. concerning regional economic development, transports and communications). These evaluations are mostly process oriented, while the effectiveness can only be assessed after some years. Performance measurement is further complicated by the fact that planning systems is only one among many influences on regional development.