Abstract: Designing immigration policy is a challenge of profound importance for destination economies around the world. Understanding how immigration impacts the economy is crucial for this task. In this article, I survey the literature on this topic and begin by explaining why estimating the impact of immigration on the economy is an empirically challenging exercise. I then show that, even among studies with convincing empirical strategies, there is far from a consensus on the impact of immigration on the wages and employment of existing workers. Immigration can sometimes lead to wage increases and better opportunities for native workers; in other contexts, it lowers wages and crowds out native employment. I end by discussing the underlying mechanisms that lead to these aggregated responses and argue that the absence of a universal relationship between immigration inflows and the economic outcomes of existing workers should not be surprising; these outcomes are determined in large part by how individual firms respond to immigration which may differ depending on local economic conditions, the types of immigrants arriving, and how those immigrants complement existing firms and workers. It is the hope that this article will be of practical help to policymakers weighing the effects of immigration on local markets.