The approach depends on what you want as the result:
x = [2008, 2009, 2010, 2011, 2012, 2013, 2014, 2015, 2016];
y = [0, 0.05, 0.1, 0.15, 0.2];
y9 = linspace(min(y), max(y), numel(x)); % Option #1
y9 = interp1(x(1:numel(y)), y, x, 'linear', 'extrap'); % Option #2
Try these and see if either of them does what you want.
