Active Labor Market Policies have been prevalent in European countries to fight unemployment. This kind of policy has been supported by many studies which find significant benefits especially for job seekers with a low risk of long-duration unemployment, e.g., young, educated job seekers \citep{Card_2010}. The program consists of a private intermediary assisting unemployed in finding a job. These private intermediaries get paid once the individual has found a stable job, e.g., a long-term contract. The central hypothesis of the paper that they want to contrast is whether the past good results overlook possible externalities. The authors argue that previous studies just match short-run labor market outcomes of the individuals that get counseled against the non-counseled ones. However, if they forget to take into account the crowding-out of the unemployed that are not in the program, in the short-run, when vacancies do not adjust, the difference in the outcomes of counseled versus non-counseled gets overestimated. Moreover, they consider that overlooking the externalities is not only crucial for the inflation of treatment effects but also for correctly judging welfare impacts of the policy. 
They follow \citet{Michaillat_2012} model that incorporates diminishing returns to scale for production technology. The model is used to generate the following hypotheses that will be contrasted later on in the specified reduced form, for more detailed information see also \citet{Landais_2010}.  Applying the model,  when a worker increases the search effort without increasing productivity per se, we find that other workers receive negative externalities since the total pool of jobs does not grow enough to absorb the extra labor supply. Hence, treatment effects should fall as the fraction of workers assigned to treatment rises since now treated workers will compete among themselves. We should expect that adverse effects are more harmful to markets where more people are treated. These externalities being stronger would also happen in markets where there is a higher competition among eligible workers. Another consequence is that externalities should be stronger when the labor market is slack like in crises periods or in markets where there is a higher unemployment rate. 
The structure of this term paper is as follows. Firstly, in section 2 it is presented a brief explanation of the experimental set-up in order to estimate the externalities. Then, each subsection describes a hypothesis derived from the model and how the researchers decided to give an answer to it. Finally,  section 3 provides a discussion of the results obtained by the authors and why is it relevant from what we have learned in the topic course.