RDP 2005-08: Declining Output Volatility: What Role for Structural Change? Equation (3)

\begin{matrix} {\tilde{σ}}_{i t}^{Y} = β_{1} {\tilde{X}}_{i t - 1} + β_{2} {\tilde{Z}}_{i t} + {\tilde{α}}_{i} + {\tilde{ε}}_{i t} & for i = 1, 2, ..., 19 \end{matrix}