Global update: USA.

Despite the political nature of stem cell research, this area of science continues to flourish in the USA. In 2011, the NIH funded approximately US$1.2 billion in stem cell research - a steady increase from past years - with US$123 million devoted to human embryonic stem cells. According to the ISI Web of Science, more than 4000 US-authored stem cell publications were produced in 2011, accounting for approximately 38% of the world total. Approximately a quarter of these publications were collaborations with authors from other countries.