OUTLIERS IN AGRICULTURE: AN INTERVENTION ANALYSIS OF AGRICULTURAL LAND VALUES
使用干预分析框架识别农业土地价格时间序列中的异常值，发现1972年的创新异常值符合投机泡沫特征，并量化了投机对土地价格增长率的影响。
Intervention analysis offers a framework for the identification and modelling of outlying observations in empirical time series. Within this framework, there are two types of outlier; an additive outlier, representing a one‐period blip in the series, and an innovational outlier, whose effect is spread over many time periods. Intervention analysis is used here to study an agricultural land price boom of the early 1970s that is generally believed to have been caused by speculative activity, and the statistical results are consonant with that view. The procedure detects an innovational outlier in the land price series at 1972 with dynamic effects that resemble the life cycle of a speculative bubble. It is inferred from these results that speculation added 52 per cent to the rate of growth of land prices in 1972, 19 per cent in 1973 and caused a fall in the rate of change in land prices of 19 per cent in 1974 and 17 per cent in 1975.