NEW YORK — Think life is not as good as it used to be, at least in terms of your wallet? You’d be right about that. The standard of living for Americans has fallen longer and more steeply over the past three years than at any time since the US government began recording it five decades ago.

Bottom line: The average individual now has $1,315 less in disposable income than he or she did three years ago at the onset of the Great Recession – even though the recession ended, technically speaking, in mid-2009. That means less money to spend at the spa or the movies, less for vacations, new carpeting for the house, or dinner at a restaurant.

In short, it means a less vibrant economy, with more Americans spending primarily on necessities. The diminished standard of living, moreover, is squeezing the middle class, whose restlessness and discontent are evident in grass-roots movements such as the tea party and ‘Occupy Wall Street’ and who may take out their frustrations on incumbent politicians in next year’s election.

IN PICTURES: The 10 happiest jobs

What has led to the most dramatic drop in the US standard of living since at least 1960? One factor is […]