Clusters and cluster policy have become a dominant paradigm in the world of both economic development theory and practice. Cluster theory suggests that firms that are part of a geographically defined cluster benefit from being part of that cluster and that these benefits result in growth in economic activity and output for the region. From here it is only a short step to argue that economic development practitioners can devise policies that can facilitate cluster development through various forms of intervention. Yet despite the large amount of writing on clusters, there is substantial vagueness and ambiguity about the concept itself as well as how clusters work to bring about economic growth and whether policies put in place to build or strengthen clusters actually achieve the desired result. In this article, the authors conduct a review of literature related to clusters to try to set forth what we know and do not know about clusters, what remains uncertain, and what the implications are for economic development practitioners.

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work is licensed under a Creative Commons IGO 3.0 AttributionNonCommercial-NoDerivatives (CC-IGO BY-NC-ND 3.0 IGO) license (http://creativecommons.org/licenses/by-nc-nd/3.0/igo/ legalcode) and may be reproduced with attribution to the IDB and for any non-commercial purpose, as provided below. No derivative work is allowed.Any dispute related to the use of the works of the IDB that cannot be settled amicably shall be submitted to arbitration pursuant to the UNCITRAL rules. The use of the IDB's name for any purpose other than for attribution, and the use of IDB's logo shall be subject to a separate written license agreement between the IDB and the user and is not authorized as part of this CC-IGO license.Following a peer review process, and with previous written consent by the Inter-American Development Bank (IDB), a revised version of this work may also be reproduced in any academic journal, including those indexed by the American Economic Association's EconLit, provided that the IDB is credited and that the author(s) receive no income from the publication. Therefore, the restriction to receive income from such publication shall only extend to the publication's author(s). With regard to such restriction, in case of any inconsistency between the Creative Commons IGO 3.0 Attribution-NonCommercial-NoDerivatives license and these statements, the latter shall prevail.Note that link provided above includes additional terms and conditions of the license.The opinions expressed in this publication are those of the authors and do not necessarily reflect the views of the Inter-American Development Bank, its Board of Directors, or the countries they represent.http://www.iadb.org 2016 1 Abstract * This paper analyzes the impact of longer school days on student achievement in Colombia. To identify the impact of longer schools days, this study exploits plausibly exogenous within school variation in the length of the school day. Using test score data from 5 th and 9 th graders in 2002, 2005, and 2009, along with school administrative data, this research uses school fixed effects models to estimate variation in average test scores across cohorts for schools that switched from a half school day to a full school day or vice versa. I find that cohorts exposed to full school days have test scores that are about one tenth of a standard deviation higher than cohorts that attended half school days. The impact of attending full school days is larger for math than for language, and it is larger for 9 th grade than for 5 th grade. Effects are largest among the poorest schools and those in rural areas. The results suggest that lengthening the school day may be an effective policy for increasing student achievement, particularly for the lowest-income students in Colombia and other developing countries.JEL Classification: I21, I28, H43

This work is licensed under a Creative Commons IGO 3.0 AttributionNonCommercial-NoDerivatives (CC-IGO BY-NC-ND 3.0 IGO) license (http:// creativecommons.org/licenses/by-nc-nd/3.0/igo/legalcode) and may be reproduced with attribution to the Inter-American Development Bank (IDB) and for any non-commercial purpose. No derivative work is allowed.Any dispute related to the use of the works of the IDB that cannot be settled amicably shall be submitted to arbitration pursuant to the UNCITRAL rules. The use of the IDB's name for any purpose other than for attribution, and the use of IDB's logo shall be subject to a separate written license agreement between the IDB and the user and is not authorized as part of this CC-IGO license. Note that link provided above includes additional terms and conditions of the license.The opinions expressed in this publication are those of the authors and do not necessarily reflect the views of the Inter-American Development Bank, its Board of Directors, or the countries they represent. Preface New technologies that are fusing the physical, digital, and biological worlds are impacting all industries, countries, and individuals. This so-called Fourth Industrial Revolution will change the way we live and transform the way we work. Preparing this and future generations of workers for a fast-changing world is not only desirable, it's essential. At the Inter-American Development Bank (IDB) we know that a key ingredient to improve lives in Latin America and the Caribbean is having the right skills to face the challenges of this new era. For this reason, we dedicated the 2017 edition of our flagship publication, Development in the Americas (DIA), to studying this topic and to proposing evidence-based solutions to address this critical problem.Undoubtedly, our region will be heavily impacted by sweeping trends around the world. Artificial intelligence, automation, the Internet of Things, 3D printing, and autonomous vehicles are not science fiction anymore. They are real and available in many parts of the world and beginning to find their way to Latin America and the Caribbean. These new trends are changing our jobs and the way we work. The full impact of these changes is still unknown, but clearly there will be a fundamental transformation in the way businesses do their business and workers do their work.A phrase by Robin Chase (co-founder of Zipcar) is telling: "My father had one job in his lifetime, I will have six jobs in my lifetime, and my children will have six jobs at the same time." Not only will our work not be a 9-to-5 job, but we will also not have the same job for our entire life. The Fourth Industrial Revolution will impose continuous and fast changes that will imply new challenges.A central challenge is how to prepare the workers of today for the jobs of tomorrow. I am optimistic because one of the region's principal assets is its people's talent. But much must be done, starting with helping the many workers in the labor force today find good jobs, and stay updated on t...

Any dispute related to the use of the works of the IDB that cannot be settled amicably shall be submitted to arbitration pursuant to the UNCITRAL rules. The use of the IDB's name for any purpose other than for attribution, and the use of IDB's logo shall be subject to a separate written license agreement between the IDB and the user and is not authorized as part of this CC-IGO license. Following a peer review process, and with previous written consent by the Inter-American Development Bank (IDB), a revised version of this work may also be reproduced in any academic journal, including those indexed by the American Economic Association's EconLit, provided that the IDB is credited and that the author(s) receive no income from the publication. Therefore, the restriction to receive income from such publication shall only extend to the publication's author(s). With regard to such restriction, in case of any inconsistency between the Creative Commons IGO 3.0 Attribution-NonCommercial-NoDerivatives license and these statements, the latter shall prevail. Note that link provided above includes additional terms and conditions of the license.