These measures eventually proved insufficient to avoid deflation. Having taken over in August 2013, Governor Mark Carney wrote his first open letter in February 2015 to explain why inflation had fallen below 1% for the first time in the MPC's history. This was followed by deflation of 0.1% in April 2015, the first month of negative CPI growth since the 1960s, and triggering a second letter. As of February 2015, Carney has written five such letters. Following the UK's vote to leave the European Union in June 2016, the MPC cut the base rate from 0.5% to 0.25%, the first change since March 2009. At the same time, it announced a further round of quantitative easing, valued at £60 billion, bringing the total to £435 billion.