what factors might cause the materials usage predictions to

what factors might cause the materials usage predictions to be incorrect

Solution

1.If a war breaks out and, as a consequence, a raw material’s supply is cut off. For example, if a major war broke out in the Middle East, the price of oil would increase, and hence the price of plastic materials would also increase.
2.If a major new discovery is made, some materials’ usage may change.
3.If defects show up in a specific material after a certain length of its service, the material’s usage may decrease. For example, a high strength composite material used for aircraft may start showing some delimitation defects.