The assessment that Europe is losing out to the US in 'brains' is overestimated, far too simplistic and based on incomplete data, a recently published study claims. It argues that in the context of increasingly knowledge-based economies, 'brain drain' is a more complex question involving many types of 'return' 'circulation' and 'recirculation' of researchers. The study, entitled 'The brain drain of PhD students from Europe to the United States: what we know and what we would like to know', examined the net balance of PhD and post-doctoral student exchanges between Europe and the US, focusing on data from four countries: France, Germany, the UK and the US. While a low level of 'mobility' was observed in the US and UK, the study revealed that higher levels of students from Germany and France are studying abroad. It also found that the influx of foreign students into the EU remains low compared to the situation in the US and Canada, which had a net balance in their favour of more than 20,000 foreign students in 2003. 'Knowledge intensive clusters', where the job opportunities are more abundant and varied, are crucial factors in explaining the migration of scientists and researchers, says the study. It refers to a survey carried out on foreign post-doctorates in French public research institutions, which concluded that in chemistry and the life sciences, foreign post doctorates made up between 30 and 50 per cent of the staff in public labs. However, according to the authors, France experiences difficulties in attracting foreign students from countries with renowned research structures. Meanwhile, American citizens prefer to stay in the US, even if measures are taken to increase their international mobility. While the data confirms pre-suppositions that the flows of students from Europe to the US, particularly for post-doctorates, is higher than that of the flow in the other direction, the study argues that existing data does not provide a complete picture of the reality on the ground. For instance, little is known about the return migration of European PhD students. Historically, about half of foreign students who earned science and engineering degrees at universities reported that they planned to stay in the US. And while these percentages seem to have increased in the 1990s, there are also indications that European researchers are returning to their home countries. In Germany, a recent survey indicated that 85 per cent of scientists who leave for work or research abroad, eventually return to jobs in Germany. However, at post-doctoral level, the evidence is scarcer as there are no data on the number of post-doctorates in Europe, making the return of EU-born post-docs from US universities difficult to assess. Moreover, uncertainty remains about the 'quality' of PhD students and post-doctorates who emigrate to the US and those who emigrate within Europe. In a number of fields, the US is without a doubt more dominant and certainly attracts talented researchers, but without more precise data the study says that it cannot back up the claim. The study argues that the strategies in place to tackle brain drain may be antiquated. An increasingly globalised knowledge-based economy has seen the emergence of a growing variety of types of return, circulation and re-circulation of brains. 'Brain circulation' refers to the cycle of moving abroad to study, taking a job there, and then returning to take advantage of a good opportunity. This form of mobility is often perceived as positive as it generates knowledge transfers and is supplementary. It should therefore not be regarded as the opposite to brain drain. Furthermore, data on this mobility trend would bring better understanding of its benefits, the study argues. The EU countries clearly lack the statistical information system on PhD graduates necessary for answering the questions essential for innovation and growth, argues the report. It adds that the lack of data is valid for nearly all issues related to the occupation and careers of PhDs. It concludes by recommending the creation of a European statistical system on PhDs, an essential tool for the implementation and benchmarking of the progress towards the European Research Area (ERA).