For example , for well over a century serious students of agriculture the world over have kept themselves busy trying to document historical changes in production indices such as seed yield ratios , yields per acre hectare , yields per laborer employed , etc . in so doing , they have often undertaken ingenious , even heroic acts of data reconstruction via interpolation and extrapolation from incomplete data 例如，一个多世纪以来，这个世界上严肃的农业学者一直忙于整理生产指数诸如种子和产量比、每英亩或公顷和产量比、人均劳动力和产量比等，以显示农业的历史变化。在从事这些项目过程中，学者们经常通过对不完整资料的内插和外推来艰苦和精巧地重建数据。
