Craft beer has become the fastest-growing - and the most competitive - segment of the global beer market. With more than 1,700 craft breweries in the UK and over 5,200 in the US, the sector has a 12.3% market share of the total beer category and is starting to present a challenge to the growth of large breweries. One way mass beer producers have fought against the bubbling competition spilling over from craft brewers is to acquire them. Anheuser-Busch InBev, MillerCoors, Constellation Brands and Heineken - which together control 81% of the US market - have all expanded their portfolios through buying smaller craft beer brands.