Here’s another myth-busting article on retirement planning. Or, more accurately, the headline claims it is a myth-busting article, busting the myth that you need a million bucks to retire.

(Is this a myth? Maybe. We see other stories that refer to it. But we find it unlikely that the million-dollar benchmark can achieve myth status when—as noted in an earlier supposed myth-busting article—less than 5 percent of the nation has that much stashed away.)

Of course, this story—from a Motley Fool writer, via an AOL finance site—doesn’t topple any myths. It just reminds you that you might need less if you factor in Social Security and any pension money. In fact, instead of busting a myth, it actually perpetuates the greatest retirement myth of all, which is that retirement planning is feasible.

It is not. After reading a dozen or so of these articles and filling in all the work sheets, the stark reality settles on you like a blanket of heavy March snow.  Fact: you can reasonably estimate neither your costs nor your income over a 25-year period. Simple as that. Any quarter-century will be riddled with booms and busts, catastrophes to you and your loved ones, all the chaos that life dishes out because that is what life does. Little wonder that so many people give up thinking about it and save as much as they can…or don’t save at all.

Lilies of the field, etc., etc.

Let us tally the unknowns:

How much income will you need the first year after retirement? This is one of the starting points in many of the retirement strategy articles and it’s actually pretty easy. It’s like predicting the weather. If you simply say the weather tomorrow will be a lot like the weather today, your odds of success are pretty good. If you needed $50,000 to live on in 2011, you’ll need about that in 2012. Unless inflation kicks up. Or you or someone close to you gets sick. Or your house gets hit by something that isn’t fully covered by your insurance. Or the car that was supposed to go another 40,000 miles doesn’t. Unfortunately, those things happen, in ways that appear random to the mortal eye. They are essentially unknowable.

How much will you need ten years from now? Well, that depends. Think just about lodging: Where will you want to live in 2022? Will you be healthy enough to live in your present house or apartment? Even if your health doesn’t degrade appreciably, will you want to look out the front window and see that same house across the street , year after year after year? What if the owner loses interest in his garden and lets the front yard go to seed? Then will you feel a desperate need to flee? What if your partner dies or leaves you?

Even if you want to stay just where you are and not change a thing, things will change around you. Prices go up. So how much do you need to factor in for inflation? For the past hundred years or so, it’s been around 3.5 percent. But there have been years when it was much higher (13.58 percent in 1980) and lower (-.34 percent in 2009). Even if you look at ten-year spans, the differences can be pronounced.

On the income side, how much can you predict about the money you’ll make on your hard-earned nest-egg? If you bought a U.S. 10-year note in September 1981, you got a yield of 15.32 percent. If you bought in September 2011, your rate was 1.98 percent.

Retirement is a crapshoot. That doesn’t mean you shouldn’t think about it.  You should. (The Chicago Tribune’s recent article, which talks about retirement not as an event but as a process with at least three stages, is a good start.) But in the end, it’s still a crapshoot. You can save too much. You can save too little. But you won’t know which you’re doing until it’s too late. It will matter to your debtors if you save too little, of course. And to your heirs if you save too much, because there’ll be a pile of cash left over. But by then you’ll be dead. Sorry.

Photo: Senior citizens find that New Ulm, Minnesota, is a good place to retire. By Flip Schulke, 1930-2008, a contributing photographer to the Environmental Protection Agency’s Project DOCUMERICA in the early 1970s, via Wikimedia Commons.