Financing Retirement: The Cistern Analogy

by: David Van Knapp

This is the final article in the mini-series on how to fund your retirement. Earlier articles were:

Essentially all strategies for financing retirement—even those as philosophically opposed as maximizing capital vs. maximizing income rights—use the same “plumbing.” I like to think of it in terms of cisterns, pipes running in and out, and leaks. The idea comes from those old algebra questions where A could fill his cistern at a certain rate, B’s cistern filled more slowly and also had a leak in it, and poor C’s cistern was a veritable symphony of problems. As a 12-year-old, you had to create formulas to figure out how long the water in each cistern would last. See Stephen Leacock’s hilarious short story, “A, B, and C—The Human Element in Mathematics.” (For younger readers: A cistern is a big barrel to collect rainwater.)

Here’s the analogy: Your retirement assets are in the cistern. There are two goals:

  • The cistern must fund your retirement adequately.

  • The cistern must never go empty. In fact, it must never get even close enough to empty that you worry about it or lose sleep over the possibility. You want a nice, abundant cistern that inspires confidence.

There is continual change in your cistern. It is not a static thing, which is why I prefer this analogy to the more common “nest egg.” The cistern’s contents expand and contract throughout your life, both before you retire (the so-called accumulation years) and after you retire (the decumulation years).

What goes into your cistern? Mostly assets that you decide to put in there. Some inflows to your retirement cistern begin early in life, while others come along later. Typical inflows include savings, 401(k) contributions, dividends, royalties, Social Security, pensions, interest, inheritances, etc.

Note that I count as inflows some items (such as Social Security) that a retiree may just spend directly. I will explain why I do this in a minute. Note also that, with the exception of old-fashioned pensions and Social Security, inflows require a positive decision on your part. You must decide to put assets into your cistern (or not).

Besides expanding from the contributions that you make into your cistern, the level in your cistern also goes up when you experience increases in the market value of assets already there. Examples of assets that may enjoy value expansion include:

  • Stocks, ETFs, mutual funds, and the like

  • Your house

  • Increasing dividends from companies that raise dividends regularly

  • A small business you may own

What about declines? It is important to note that declines in the level of the assets in your retirement cistern take place not only after retirement via actual withdrawals, but earlier in life as well. Some people “raid” their cistern prior to retirement to cope with emergencies or to make large purchases. Taking out a home equity loan to buy a boat, for example, decreases the level of your cistern in two ways: First, the value of the loan lowers your equity in your home and thus decreases its value in your cistern. Second, the additional debt creates interest obligations that reduce the amount you can put into your cistern for some time into the future.

The level in your cistern also goes down if the value of the assets in it declines. Significant declines in the value of your stocks or your home obviously can have a major impact on the level in your cistern. During the recent financial crisis, some people have been forced to delay long-planned retirements, because the levels in their cisterns went down so far that the two major goals—seemingly within their grasp—suddenly were moved out of reach.

And everybody’s cistern has a leak: Inflation. That is a continuing outflow, sometimes rapid, sometimes slow, that insidiously reduces the value of the contents of your cistern. Only if we go into a period of deflation would the value-of-money dynamic actually cause the value of what’s in your cistern to expand. It would become like an inflow rather than a leak.

I said that I would explain why I count as inflows monies that go directly to spending, such as Social Security payments. The reason is that if we visualize that everything runs through the cistern, even if only briefly, it puts all assets on an equal footing for analysis. The value of income rights can be directly compared to the value of capital, for example.

Viewed this way, everyone makes withdrawals from their cisterns. Thus, someone who spends his Social Security check upon arrival must acknowledge that if he did not spend all of it, he could deposit the balance in his cistern for a future day. And the debate between income-maximizing strategies and capital-maximizing strategies can be seen for what it really is, which is an assessment of two strategies, both of whose goals are the goals stated at the beginning of this article. In both cases, the retirees are betting that their strategy will both provide sufficiently for retirement and that their cistern will never run dry.

Say someone maximizes income during their accumulation years by loading up on dividend-paying stocks, then lives off the income in retirement. We can picture the dividends as flowing into the cistern through a dividend pipe, but flowing right back out through a dividend-withdrawal pipe. Such a person might say that she is not making “withdrawals” if they just take the dividends directly, but she really is, because if not taken immediately as cash, the money would flow into the cistern. The same reasoning applies to pension or Social Security income. You may take it directly, but it is helpful to view it as flowing into and out of the cistern. It provides a better picture of the dynamics of retirement funding.

Similarly, someone who loads up on growth stocks during their accumulation years, then converts those assets into income by selling portions to fund retirement, is clearly making withdrawals. The “bet” is whether the unsold assets remaining in the cistern will simultaneously expand enough to make up for the assets sold. Similar reasoning applies to someone who buys an annuity: She makes a big withdrawal to buy the annuity, but the annuity itself then creates an inflow of income that lasts the rest of her life. The “bet” is whether the income will eventually exceed what it cost to purchase the annuity.

So the cistern analogy is strategy-neutral. I believe that viewing retirement funding in this way allows for more reasoned comparisons of strategies. It’s no secret that I believe in the efficacy of accumulating assets that bear rights to receive increasing dividends, and that I think that it is a superior retirement strategy to relying principally on accumulating assets that hopefully will expand in value via increasing prices to offset withdrawals. But I do not kid myself that when I spend those incoming dividends or Social Security checks, I am not really draining a little bit out of my cistern each time too.

Disclosure: No positions mentioned