I am studying the determinants of unemployment spells. My dependent variable is unemployment spell (duration of unemployment), which comes in months. such as less than 1 month, 1 month & above but less than 3, 3 months & above but less than 7, 7 months & above but less than 10, and lastly 10 to 12 months. I am in a fix as to how to fit a model for this kind of analysis. Help would be really appreciated. Thanks