ABSTRACT
Since AYL has no trend, the tiifk~.criciui?; o p e ~ t i o n can 1)c consitlered as a cletrending device. This is all inlportarit, fe;ature of the Box-Jerkins tiinc scrics analysis packages. Thc "'err,or-cor~,ectiol? for~ii" of' (20.5.1) is
Granger (1981) suggcstetl that although nimy economic time series appear as 1 ( 1 ) , linear. cornbinat,ions of thcsc mriables rrlay be T ( 0 ) ; that is, sorric relittions betweeii variables are stationary. 13e citllcd rnodels for such variables "cointegraled."
