NonlinearbehavioroftheChineseSSECindexwithaunitroot:Evidencefromthresholdunitroottests,钱夕元,宋福铁,WeinvestigatethebehavioroftheShanghaiStockExchangeComposite(SSEC)indexfortheperiodfrom1990:12to2007:06usinganunconstrainedtwo-regimethresholdautoregressive