type="main" xml:id="jtsa12058-abs-0001" <title type="main">Abstract</title>This article first studies the non-stationarity of the first-order double AR model, which is defined by the random recurrence equation <math xmlns="http://www.w3.org/1998/Math/MathML" display="block" altimg="urn:x-wiley:01439782:media:jtsa12058:jtsa12058-math-0001" wiley:location="equation/jtsa12058-math-0001.gif"><msub><mrow><mi>y</mi></ mrow><mrow><mi>t</mi></mrow></msub><mo class="MathClass-rel">=</mo><msub><mrow><mi>φ</mi></mrow><mrow><mn>0</mn>< /mrow></msub><msub><mrow><mi>y</mi></mrow><mrow><mi>t</mi><mo class="MathClass-bin">−</mo><mn>1</mn></mrow></msub><mo class="MathClass-bin">+</mo><msub><mrow><mi>η</mi></mrow><mrow><mi>t</mi>< /mrow></msub><msqrt><mrow><msub><mrow><mi>γ</mi></mrow><mrow><mn>0</mn></m row></msub><mo class="MathClass-bin">+</mo><msub><mrow><mi>α</mi></mrow><mrow><mn>0</mn>< /mrow></msub><msubsup><mrow><mi>y</mi></mrow><mrow><mi>t</mi><mo class="MathClass-bin">−</mo><mn>1</mn></mrow><mrow><mn>2</mn></mrow></msub sup></mrow></msqrt></math>, where γ₀  0, α₀ ≥ 0, and {η_t}is a sequence of i.i.d. symmetric...<//msub></msubsup><//m></mrow><//></mrow>

Two of the fastest growing frontiers in econometrics and quantitative finance are time series and financial econometrics. Significant theoretical contributions to financial econometrics have been made by experts in statistics, econometrics, mathematics, and time series analysis. The purpose of...