Don’t look now, but the transition to a mobile-centric computing culture in the U.S. is now certified.

Let’s check some new data points that represent several crossed Rubicons in the march toward Mobile Nation:

For the first time, most Americans in every age group are smartphoners. According to new stats reported today by Nielsen, the age group threshold was crossed in the first quarter. Fifty-one percent of the holdout group — those over the age of 55 — now possess a smartphone, so age is no longer the big factor it was in smartphones’ march to dominance.

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