When President Obama delivered his first State of the Union address in 2009, 53% of Americans considered themselves middle class. Six years later, just 44% of Americans define themselves that way.

It’s no secret working Americans have been under duress for more than a decade, as wages stagnate, computers and robots displace human workers and wealth becomes concentrated among an alarmingly small portion of the population. Obama has promoted policies meant to help the middle class throughout his six years in office, yet the problem today is quite different than when he started the job in 2009—and it’s not clear Obama fully grasps the change.

The president's latest proposal to aid the middle class is a “Robin Hood” tax plan that would hike taxes on the wealthy to finance tax cuts for lower earners. Transferring money from the rich to the working class through the tax code has been a recurring theme of Obama’s (and many Democrats’) tax proposals. And his latest plan seems no more likely to pass a Republican-controlled Congress than many other ideas that have starred in a State of the Union address, then quietly retired.

The middle class itself, however, has changed notably during the relatively short time Obama has been in office, as the chart below shows. The portion of Americans who consider themselves middle class has dropped (as has the portion considering themselves upper class), while the ranks who call themselves lower class have swelled.

Percentage of adults self-identifying as each social class:

Americans are less optimistic than they used to be, with the Harris “alienation index ”—which measures satisfaction with five different elements of public life—at the worst level in the poll’s 39-year history. The government’s approval ratings remain close to record lows, and a startling majority of Americans still feel the nation is headed in the wrong direction.

What’s striking about the sour mood is that it has persisted throughout an economic recovery that’s now in its sixth year, with 2014 being an especially strong year for job growth. Obama has correctly identified many economic factors that dog working families—such as flat pay, a shortage of digital-era skills, and the high cost of child care, college and healthcare—but there’s something else going on that Obama’s various proposals for the middle class don’t capture: Too many Americans seem to be losing hope in a bright economic future.

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There's no set definition of "middle class." It might consist of families between the 25^th and 75^th income percentiles, or between the 20th and 80th income percentiles, which would roughly equate with household income ranging from $25,000 to $105,000. But there are many subjective factors that contribute to a middle-class lifestyle and aren’t easily measured. Many people with incomes in the top 10% of earners, for instance, consider themselves middle class, because they work for their income instead of living off investments and come from modest circumstances.

A 2010 report commissioned by Obama himself declared that “middle-class families are defined by their aspirations more than their income.” And it’s those aspirations that may be the most threatened element of a middle-class lifestyle today.