Tachizawa and Thomsen (2007) empirically investigated the aspects of flexibility related to the upstream SC. The results show that firms need supply flexibility for a number of important reasons (manufacturing schedule fluctuations, JIT purchasing, manufacturer slack capacity, a low level of parts commonality, demand volatility, demand seasonality and forecast accuracy), and that companies increase this type of flexibility by implementing two main strategies: "improved supplier responsiveness" and "flexible sourcing". The results also suggest that the supply flexibility strategy selected depends on the type of uncertainty (mix, volume or delivery).