This monograph aims to collect together recent theoretical insights and various empirical results for a rapidly developing area concerning the analysis of business and economic forecasts. Strictly following econometric textbooks, it is tempting to assume that forecasts are the result of a careful modelling exercise, and that the econometric model-builder delivers the forecast to an end-user. However, since the mid 1980s the literature has contained various studies which suggest that the model-builder is not always the last person to deal with the forecast, and there can be someone in between the model-builder and the end-user, whom I will call the expert. This expert can modify or adjust the model forecast, after having received it and evaluated it, and it is this adjusted forecast which is typically delivered to the end-user. The early literature contains some scattered examples where such an adjustment occurs, sometimes to the benefit of the quality of the forecast, but sometimes not. Recent literature shows a revived interest in these expert-adjusted forecasts, for various reasons. First, and as will be argued in this book, it turns out that many, if perhaps not all, economic forecasts seem to undergo some tweaking from an expert. The recent availability of very large databases with expert-adjusted forecasts and model forecasts emphasizes this outcome. Second, there is a revived interest in analysing the quality of economic forecasts, and when experts have adjusted econometric model forecasts it may be necessary to rethink how such final forecasts should be evaluated. Third, it will be interesting to understand what it is that an expert does, in particular in cases where they themselves do not say. Below we will see that there are many possible reasons for experts to modify forecasts, and in this book I aim to put the experts’ behaviour into an econometric perspective. I will argue that adjusting model forecasts can be quite a good idea, and there are some potentially useful guidelines. It is hoped that this book will rouse the interest of academics and practitioners to pursue further research and obtain practical experience in order to learn how to create useful and reliable forecasts.