why zinb iterations are not concave in a flow chart how do you know if an interval is concave in zinb does zinb converge why does the model not converge why is zinb concave iterations why does zinb model not converge when you drop zinb model, iterations continue to be not concave what model does zinb use why is zinb model not concave why does zinb model not concave why does my zip model not have concave iterations why are not its iterations of zinb concave? why is zinb not concave after iteration why not concave iterations in zinb what model will not concave when truncate why is my model not concave how to make iterations that are not concave does zinb have iterations why is model not concave in zinb? why is it not always concave in a zinb model?