BBH offers a more concentrated take on the global biotech industry. Although the space is already dominated by US firms, the fund aims to select just 25 US listed companies by market cap, also weighing each constituent by market cap. The underlying index has a flexible definition of biotech, encompassing companies engaged primarily in research (including research contractors) and development as well as production, marketing and sales of drugs based on genetic analysis and diagnostic equipment, excluding pharmacies. Also, despite capping its issuers to a maximum of 20%, the fund may still be top heavy due to the indexs concentrated nature. Overall, BBH is a viable take on this market. The index is reviewed semi-annually.