The middle class is on the decline across the wealthiest countries in the world and the shift is hitting the youngest generations hardest, according to a new report published by the Organization for Economic Cooperation and Development (OECD).

Today, just 60% of millennials (those born between 1983 and 2002) are considered middle-class, compared to 70% of baby boomers (those born between 1943 and 1964) when they were in their twenties, according to the report, "Under Pressure: The Squeezed Middle Class." Worldwide, the share of households considered middle-class has slipped from 64% in the 1980s to 61% today.