The percentages of happiness

"Knowing someone who is happy makes you 15.3% more likely to be happy yourself, the study found. A happy friend of a friend increases your odds of happiness by 9.8%, and even your neighbor's sister's friend can give you a 5.6% boost... A happy friend who lives within a half-mile makes you 42% more likely to be happy yourself. If that same friend lives two miles away, his impact drops to 22%... Happy spouses provide an 8% boost -- if they live under the same roof. Next-door neighbors who are happy make you 34% more likely to be happy too, but no other neighbors have an effect, even if they live on the same block."— British Medical Journal