Zipf's Law everywhere

At the 100th anniversary of the birth of George Kingsley Zipf, one striking fact about the statistical regularity that bears his name, Zipf's law, is that it seems to appear everywhere. We may ask these questions related to the ubiquity of Zipf's law: Is there a rigorous test in fitting real data to Zipf's law? In how many forms does Zipf's law appear? In which fields are the data sets claiming to exhibit Zipf's law? Keywords: Zipf ́s law, ranking, language, population, internet, economics, bibliometrics, natural phenomena 1. Testing Zipf's law against alternative functions Claiming a Zipf's law in a data set seems to be simple enough: if n values, xi (i =1,2, …,n), are ranked by x1 ≥ x2 ≥ … xr … ≥ xn, Zipf's law states,