Middle income countries (MICs) are facing rapidly evolving development challenges as their economist mature and integrate into the global economy. As a group, the 86 MICs account for about one -- fifth of world output, and their per capita income has grown by almost 4 percent annually since 1995. Yet there are still home to one -- third of the world's poorest citizens, living on less than $2 per day. The World Bank has provided US$163 billion in loans to these countries since 1995 and it allocates about half of its administrative budget to working with them. Today, as a group these countries have far more choice than they did even 10 years again obtaining both finance and knowledge for development. With the dramatic changes in the global context, many stakeholders and outside commentators have began to propose that the Bank change its relationship with this group -- with proposals ranging from strengthened engagement to withdrawal. This IEG evaluation brings a fresh perspective to the debate by assessing the development effectiveness of the Bank's recent work. It presents evidence -- including views from the client countries themselves -- about the outcomes of the Bank's support to individual countries over the pats 12 years. It also spotlights three growing dimensions of the Bank Group's role -- sharing knowledge across countries, engaging countries in global programs, and combining support to the public and private sectors.