Abstract
The question we discuss is whether a simple random coefficient autoregressive model with infinite variance can create the long swings, or persistence, which are observed in many macro economic variables. The model is defined by y_{t}=s_{t}¿y_{t-1}+e_{t}, t=1,…,n, where s_{t} is an i.i.d. binary variable with p=P(s_{t}=1), independent of e_{t} i.i.d. with mean zero and finite variance. We say that the process y_{t} is persistent if the autoregressive coefficient ¿_{n} of y_{t} on y_{t-1}, is close to one. We take p<1<p¿² which implies 1<¿ and that y_{t} is stationary with infinite variance. Under this assumption we prove the curious result that ¿_{n}¿¿¿¹. The proof applies the notion of a tail index of sums of positive random variables with infinite variance to find the order of magnitude of ¿_{t=1}ny_{t-1}² and ¿_{t=1}ny_{t}y_{t-1} and hence the limit of ¿_{n}
Originalsprog | Engelsk |
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Tidsskrift | Journal of Econometrics |
Vol/bind | 177 |
Udgave nummer | 2 |
Sider (fra-til) | 285-288 |
Antal sider | 4 |
ISSN | 0304-4076 |
DOI | |
Status | Udgivet - apr. 2013 |