Most retirement calculators are optimistic to a fault. They assume our incomes will rise throughout our working lives, or at least stay roughly the same.

In reality, our incomes are likely to peak years – and sometimes decades – before we retire. Consider this:

• People’s biggest wage increases tend to happen in their 20s and 30s, with more modest increases in midlife followed by declines, a 2016 analysis of Social Security earnings records underwritten by the Federal Reserve Bank of New York finds.

• Most people’s incomes peak by age 45, the researchers found, although the top 20% of earners peaked in their 50s.

• More than half of those who enter their 50s with a stable job are laid off or otherwise forced out the door, and the vast majority don’t recover financially, analysis by ProPublica and the Urban Institute finds.

These may be grim statistics, but if you’re tempted to put off saving for retirement, take heed.

“When you’re 40 and things are going well, you think, ‘OK, I can see when things are going to get better and that’s when I can save for retirement,’” says Gary Burtless, an economist with the Brookings Institution who studies earnings patterns. “And those days just don’t come.”

Biggest gains come early

What’s true on average for a group of people may not be true for an individual, of course. Understanding these general patterns, though, could help people make better decisions about spending, saving and when to retire.

Generally, the more education people have, the more money they make over their lifetime and the later their earnings peak, Burtless says.

“For somebody with a position like professor at a university, it might be when they’re in the second half of their 50s, as opposed to the second half of their 30s, which it might be for your brother-in-law who failed to complete high school,” Burtless says.

But the 50s tends to be a dangerous decade for workers, according to ProPublica, an independent nonprofit newsroom, and the Urban Institute, a nonprofit think tank that researches social and economic issues.

The researchers found 56% of full-time, full-year workers ages 51 to 54 suffered an involuntary job loss after age 50 that had a substantial economic impact, either by reducing their earnings at least 50% or resulting in six months or more of unemployment. The median household income of these workers dropped 42%, and only one in 10 ever earned as much after they left their jobs as before. An additional 9% left their jobs involuntarily for personal reasons such as health. The analysis was based on data from the University of Michigan Health and Retirement Study, which tracks 20,000 people in the U.S.

Save early, avoid lifestyle creep

Job disruptions and declining earnings help explain why so many people in their 60s have so little saved, Burtless says.

“Instead of having those last years when you no longer have children in the house to bulk up your savings, you are using up your savings even before you reach retirement age,” he says.

People entering their 50s without having saved enough for retirement may need to plan to work longer, or cut their expenses, rather than assume rising incomes will help them make up the deficit, says certified financial planner Michael Kitces, who blogs at Nerd’s Eye View.

Kitces advises people in their 20s and 30s to commit to putting half of their raises into retirement funds. Since those raises are likely to be largest in the early years, saving half can jump-start retirement funds while limiting “lifestyle inflation,” or the tendency to spend more as income increases.

It can be tempting to take on a big mortgage, for instance, thinking that future salary boosts will make the payments more manageable, or to celebrate a raise by buying a fancier car. If your income doesn’t rise – or starts to drop – it can be painful to downsize or go back to plainer vehicles. (Also, the more expensive your lifestyle, the more money you’ll need to retire.)

“Recognize that it’s a lot harder to remove something from our lives than it is to just not add it to our lives in the first place,” Kitces says.

Liz Weston is a columnist at NerdWallet, a certified financial planner and author of “Your Credit Score.” Email: [email protected]. Twitter: @lizweston.