Well, ignoring the rather loose way in which we (the west) have been using the term 'defending' in the last few years, I would agree that these figures may well be a bit skewed - similar graphs breaking down exactly what the spending is used for would be far more useful.

For example, I don't have the figures, but I would assume that the USA spends an awful lot more on military R&D than the nations here in Europe, and subsequently is likely to see something of a return when we decide we need a new line of state-of-the-art fighter jets or similar. It doesn't look like the potential returns on the spending have been taken into account in the data, here, which somewhat obscures their significance.