Americans are not talking about the fact that they do not have enough money to retire, according to Northwestern Mutual.

A lack of communication may be one of the reasons working Americans do not have the money set aside to retire, Northwestern Mutual said in its 2015 Planning and Progress Study, released Monday.

Forty percent of adults out of the 5,474 surveyed said they have not discussed retirement with anyone, and 35 percent do not have any sense of how much income they will need to retire.

Of those who anticipate working beyond the traditional retirement age of 65, 62 percent say it will be from necessity because they are not saving enough or do not trust Social Security to be there.

“Working past retirement age should be a personal decision rather than a default financial planning strategy. Employment opportunities and personal health as we experience them in our 50's don't always hold true in our 60's and beyond,” said Rebekah Barsch, vice president of planning at Northwestern Mutual. “With life expectancy increasing, planning for retirement is essentially like preparing for a vacation that could last decades.”

Of those who will continue or are continuing to work beyond retirement age by choice, most say they enjoy their job, want additional disposable income or want the social interaction a job brings.

Out of the adults who are still working, 68 percent expect to be happy in retirement, compared to 80 percent of current retirees who say they are happy. Similarly, 52 percent of future retirees expect to be able to maintain their quality of life in retirement, compared to 61 percent of current retirees who have managed to do so.

This somewhat pessimistic outlook may stem from shortfalls in financial planning, said Northwest Mutual. The data reveals that adults who consider themselves highly disciplined or disciplined planners are significantly more likely to be happier before and during retirement and better equipped to manage unexpected situations, than those who consider themselves informal planners.