A quality certification standard in a competitive setting can improve welfare but may affect consumers and producers differently. In a competitive model with quality preferences of the vertical product differentiation type, we find that producers prefer a higher (lower) quality standard than...

We suggest a new unit-root test with a Fourier function in the deterministic term in a Dickey–Fuller type regression framework. Our suggested test can complement the Fourier LM and DF-GLS unit root tests. They have good size and power properties.