I read this blurb in our paper today, and wonder how they know. I didn't find anything on how they did the research, but the idea intrigues me:
For those who think the world is obsessed with "time," an Oxford 
dictionary added support to the theory today in announcing that the word is the most often used noun in the English language.
"The" is the most commonly used word overall, according to The Concise Oxford English Dictionary.
The list of top 25 nouns: time, person, year, way, day, thing, man, world, life, hand, part, child, eye, woman, place, work, week, case, point, government, company, number, group, problem, fact.
