# Why did the hybrid Phillips Curve become flatter (as empirical data shows) after the crisis?

The Phillips Curve equation is: $$\pi_t=\pi_t^e + \beta_1 (\beta_2 Y_t + (1-\beta_2) Z_t) + \varepsilon_t^\pi$$ where $\pi_t$ is the inflation, $\pi_t^e$ is the expected inflation, $Y_t$ is the output level, $Z_t$ is the real exchange rate, and $\varepsilon_t^\pi$ is a stochastic shock.

In a small open economy (semi-structural framework), the impulse response functions to a domestic demand shock are the following:

After the crisis, the Phillips Curve became flatter. My question is, how can one interpret the change in the slope of the Phillips Curve after the crisis?