WASHINGTON — The income gap between the wealthiest 20 percent of American households and the rest of the country grew sharply in 2011, the Census Bureau reported, as an overwhelming majority of Americans saw no gains from a weak economic recovery in its second full year.

Income for the top fifth of American households rose by 1.6 percent last year, driven by even larger increases for the top 5 percent of households, said David Johnson, the Census Bureau official who presented the findings. All households in the middle of the scale saw declines, while those at the very bottom stagnated.

“You’re really struck by the unevenness of the recovery,” said Lawrence Katz, an economics professor at Harvard. “The top end took a whack in the recession, but they’ve gotten back on their feet. Everyone else is still down for the count.”