Why is it that the I Love NY slogan, which was designed more than 30 years ago, is still so popular that it generates $30m a year in royalties for New York City. An explanation was given on the radio today by the man who designed it, Milton Glaser. He said that the secret of its success was that when someone saw the design for the first time its meaning wasn’t immediately obvious, that it was a puzzle which they had to decipher and when they did, they felt a warm glow of achievement. The memory of this warm glow would subconsciously return every time they saw it. Mr Glaser also revealed that he had expected the campaign to last for only a few weeks and had agreed to give the design to New York City as a pro bono gesture, and so isn’t entitled to any share of the annual $30m royalties. I wonder what sort of memory that invokes- not a warm glow I’d guess.