The following chart plots the FTSE 100 Index for the period 1 January 2016 to 11 July 2016. It also plots the Index priced in US dollars (i.e. it shows the returns a US dollar investor would see over this period).
Today, the FTSE 100 Index closed at 6682, an increase of +9.7% from 1 January 2016.
Adjusted for the GBPUSD rate, the FTSE 100 closed today at 5886 (in dollar terms), a decrease of -5.7% on the start of the year.