Imagine a millennial fretting about the rising cost of avocado toast on the way to work, circa 2062. It's the scenario being floated by a new study from Aon that says millennials are already behind in their retirement saving. The report from the risk, retirement and health consulting provider says most won't be able to retire until age 70 or later. First, let's talk about savings rates. It's a boring old message we've heard thousands of times. Yet it's true. Save more.

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If you can, that is. Given wage stagnation, student loans and competing financial goals, it's not always easy to save the recommended 10 percent to 15 percent of income.

When saving is a challenge

Saving for retirement is a bumpy road for Katie Rucke Utterback, 28. First, she worked for a company that ran into financial difficulties. She had been saving in her company's 401(k) plan at 4 percent in order to get the match. When the company hit hard times, they cut salaries and then ended the employer match. Utterback has a new job as content writer for a non-profit credit counselling agency and is again saving at 4 percent. To date, she has saved about $1,000. Both accounts total around $2,000: "Not even one month's salary," Utterback said.

Utterback's husband works in IT and, even with his income, most of the couple's money goes toward renting their $2,500 a month apartment. High daily expenses and wage stagnation make it hard for Utterback to save more. "Our pay hasn't caught up," she said. "I personally feel that I'm behind. "I have about $9,000 of credit card debt; I'm not going to the bar every day, I don't drink coffee out and we make all our meals at home," she said. "Our entertainment is Netflix." Stock market volatility and the seeming fragility of Social Security, Medicare and Medicaid are huge concerns, she says. "Can we even afford to have kids?" she said. "How do we pay for them to live and make sure we're OK when we're older? "It feels like we're having to make decisions that our parents didn't have to make," she added. One issue is people's reluctance to discuss personal financial situations. "Money is more taboo than talking about our sex life," she said. "I'm trying to be more vocal about trying to break that taboo." Her friends have appreciated her openness and say it makes them feel less alone.

These days, her friends bring their own bottles of wine and hold game nights at each other's houses. "If we had financial literacy programs in high school, middle school, elementary school, it wouldn't be such a huge issue," Utterback said. "That knowledge is so powerful."

Saving can come later