#personal finance

There is an appealing simplicity to saying that 85% of a portfolio will be invested for the long term while 15% will be reserved for individual ideas.

The difficulty begins approximately five minutes later.

What happens when one of the individual stocks doubles? What happens when several of them fall? Does the investor restore the original percentages in both cases? Can new money refill the speculative account? When does a successful position stop being an experiment? And what prevents a temporary 15% allowance from slowly becoming half the portfolio?

These questions matter because an allocation is not yet a system. An allocation describes how a portfolio looks on one day. A system describes what happens next.

In A Budget for Speculation: Can Stock Picking and Passive Investing Coexist?, I argued that some investors may be better served by giving speculation a limited budget than by pretending they will never feel tempted to speculate. Most of the portfolio performs the sober work of long-term wealth building. A smaller portion provides room for individual ideas, intellectual curiosity and the occasional attempt to be right in a more interesting way.

The behavioral premise was simple: the appetite gets a plate, not the pantry.

This companion article is about building the plate.

First, distinguish the general strategy from the ratchet

Core–satellite investing is a broad family of portfolio designs. The core generally consists of diversified, long-term holdings. The satellites are smaller positions used to pursue active ideas, specialized exposures or other objectives not fully represented in the core.

Americans spend a great deal of money on cars, but we have developed a convenient way of not thinking about the total.

The payment comes from one account. Insurance arrives on another date. Gas disappears twenty or fifty dollars at a time. Tires show up every few years with the impeccable timing of a dental emergency. Registration is somebody else's problem until suddenly it isn't. Then one morning the transmission starts making a sound ordinarily associated with farm machinery.

Each expense seems to be its own small incident.

Wealth, unfortunately for anyone trying to measure the damage, works in the opposite direction. Small amounts of money combine. Savings earn returns. Those returns can earn returns. Time takes a few hundred dollars a month and, given enough years, does something almost indecent with it.

Which raises a question worth asking:

What would Americans be worth if cars simply cost less?

Not if everybody gave up driving. Not if the suburbs were bulldozed tomorrow morning and replaced with bicycle paths and espresso bars. And not if Americans suddenly stopped liking cars.

Just: what would happen if getting around took a smaller bite out of the household budget?

The answer may be considerably larger than the monthly savings suggest.

The almost-$1,000-a-month machine

AAA has been trying to answer a deceptively simple question for more than 70 years: what does a new car actually cost to own?

There is a wonderfully boring argument for how to build wealth in the stock market.

Buy a diversified collection of productive businesses. Keep buying. Reinvest the dividends. Avoid panicking. Wait a very long time.

For most individual investors, broad-market index funds make this remarkably easy.

There is only one problem.

Stock picking is fun.

Not for everybody, certainly. But for a particular kind of investor, researching individual companies scratches an itch that an index fund simply doesn't. There is a puzzle to solve. A judgment to make. A possibility that everyone else has missed something.

Maybe a company is temporarily unpopular. Maybe a promising business is buried beneath ugly quarterly numbers. Maybe the market has underestimated some technological change. Maybe you have found the proverbial $10 bill lying on the sidewalk.

And, hovering somewhere behind all that sober analysis, there is another possibility:

What if this one really takes off?

This creates a peculiar conflict.

The investor may intellectually believe that diversified, long-term investing is the more dependable path to wealth while simultaneously finding individual stocks much more interesting.

The usual solution is straightforward: suppress the second impulse.

But perhaps there is another possibility.

Instead of trying to eliminate the desire to speculate, give it a budget.

Two jobs that investing can accidentally acquire