Retirement preparedness is a problem for every generation, with a recent survey from Aon revealing that just one in three workers are financially prepared for their post-working life. 

Millennials, however, face some additional obstacles that don't apply to their older counterparts. In particular, Aon has identified three specific challenges that will make it much harder for millennials to achieve retirement security -- and will necessitate that millennials save more than past generations. 

What are those three challenges? Read on to find out. 

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1. Medical inflation

Medical inflation is far outpacing wage growth. This puts pressure on working millennials struggling to save as they pay an ever-increasing portion of their salaries for health coverage and healthcare.

It also means medical care will likely cost much more when millennials reach retirement age unless big -- and politically challenging -- changes occur.

With estimated healthcare costs already in the hundreds of thousands for today's seniors, millennials will need to save a fortune just to cover the medical expenses they're likely to face in old age. 

2. Absence of a traditional pension

Pensions once made up part of a "three-legged" stool, along with Social Security and savings, that helped to fund a secure retirement.

Traditional pensions have all but disappeared, so very few millennials will be able to rely on this guaranteed source of lifetime income. Social Security alone isn't enough to fund a secure retirement, so millennials will need to step up their own retirement account contributions to make up for the absence of a pension. 

Young people working in the gig economy may also not have a traditional workplace 401(k) either, so may be left without employer matching contributions that can help to boost account balances.

3. Rising life expectancy

Increasing life expectancy is a good thing, but it means saving needs to last longer so retirement account balances need to be larger. With people living longer, there's also a greater need for healthcare later in life -- which drives a need for even more funds. 

What can millennials do to prepare?

To deal with these three challenges head on, younger people will likely work longer to ensure they amass the funds they'll need.  In fact, Aon estimates millennials likely won't have the funds to retire comfortably by 67 so will need to keep working longer into traditional retirement age.

Millennials also need to update their expectations regarding the necessary amount of retirement savings. While financial advisors traditionally recommend saving 10 times your final salary by retirement, Aon estimates that those in their 20s need to save 12.5 times their final salary to retire comfortably. Those in their 30s today will need 11.5 times their final pay. 

Millennials should up their savings rates today

Coming to terms with these challenges now and working to put aside a larger percentage of income could help millennials to be better prepared so they can leave the workforce when they're ready and enjoy the retirement they deserve.

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