The US is experiencing a "brain gain", with more than 1 million skilled immigrant workers competing for 120,000 permanent US resident visas each year, a report from three US universities suggests. Researchers from Duke University, New York University and Harvard University say that foreign nationals living in the US contributed to more than a quarter of new inventions with patents filed last year. "Resident aliens" contributed to more than half of all the international patents filed by a number of large multinational companies, including Qualcomm, GE, Siemens USA and Cisco Systems. In addition, 41 per cent of patents filed by the US Government had foreign nationals as inventors or co-inventors, the report shows. The researchers say the loss of foreign-born inventors would be detrimental to the US's economic wellbeing.