Mature products with stable demand are usually easiest to forecast. Staple products at a supermarket, such as milk or paper towels, fit this description. Forecasting and the accompanying managerial decisions are extremely difficult when either the supply of raw materials or the demand for the finished product is highly variable. Some examples of items that are difficult to forecast include fashion goods and many high-tech products. Good forecasting is very important in cases because the time window for sales is narrow and if a firm has over-or underproduced, it has little chance to recover. For a product with a long life cycle, in contrast, the impact of a forecasting error is less significant.