Retirement Portfolio Basics: 401(k)s, IRAs and the 4% Rule

Which account, and what goes in it? Those are the two questions. Most people can settle both in an afternoon. Then leave the whole thing alone for years. The account decides what you pay in tax. What you hold inside it decides how the balance behaves in a bad year, and whether you are still holding it when the good years arrive.

The order to fill things in

1. Contribute enough to the workplace 401(k) to collect the full employer match.
2. Clear high interest debt, because no portfolio reliably beats a credit card rate.
3. Build an emergency fund in cash, so a bad month never forces a sale.
4. Fund an IRA, where the choice is wider and the costs are often lower.
5. Go back to the 401(k) and push contributions toward the annual limit, which the IRS sets and adjusts, so check the figure for the current year before you plan around a number you read somewhere.
6. Use a taxable brokerage account for anything beyond that.

Steps two and three are the ones people skip. They are the reason the rest works. An emergency fund is not an investment decision. It is the thing that stops a broken car from becoming a fund sale at the worst possible price.

What the match is worth, in one payslip

Take a $60,000 salary. The plan matches 50 cents on the dollar for the first 6 percent of pay.

Contribute 6 percent and you put in 0.06 x 60,000 = $3,600, and your employer adds 0.5 x 3,600 = $1,800. Your $3,600 starts work as $5,400 before a single market return.

Contribute 3 percent instead. You put in $1,800, receive $900, and leave $900 sitting on the table for that year. It does not roll over. It is simply not paid.

Pre-tax or Roth

Account	Money going in	While invested	Money coming out
Traditional 401(k) or IRA	Pre-tax, lowering this year’s taxable income	Grows without annual tax	Taxed as ordinary income
Roth 401(k) or IRA	After-tax, no deduction	Grows without annual tax	Qualified withdrawals are federally tax free
Taxable brokerage	After-tax	Dividends and realized gains taxed yearly	Only the gain is taxed

A $6,000 pre-tax contribution for someone in an illustrative 24 percent bracket reduces this year’s federal tax by 6,000 x 0.24 = $1,440, and the whole balance gets taxed on the way out decades later. The same $6,000 into a Roth gives you no deduction now and hands you the growth free of further federal tax.

Someone early in a career, with income likely to rise, often leans Roth, while someone in their highest earning years, wanting the deduction while the rate is high, often leans pre-tax. Holding both means the guess does not have to be right, and it gives you two differently taxed pots to draw from later, which is quietly valuable. The wider picture is in tax-efficient investing.

What goes inside the containers

An account is a container. The investments sit inside it. The target mix from asset allocation applies to every account added together, as one combined total.

Two routes work for almost everyone. One is a single target-date fund that holds the entire portfolio and manages itself, and the other is two or three broad index funds, typically a total US stock fund, an international stock fund and a bond fund, in the proportions you chose.

Cost matters here more than anywhere else. This money compounds for decades. Take $100,000 left alone for 30 years at a 7 percent gross return. At a 0.03 percent expense ratio it grows to about $754,849. At 0.60 percent it grows to about $643,056. That is roughly $112,000 of difference for an identical investment, and you can check it on your own funds with the expense ratio calculator.

Glide paths, and what they quietly assume

A glide path is the schedule by which a target-date fund reduces stock exposure as its year approaches, and the shape below is illustrative, since every fund family publishes its own.

Age	Stocks	Bonds and cash	What it assumes about you
30	90%	10%	Decades of contributions still to come
45	80%	20%	Balance now bigger than your annual saving
55	65%	35%	Sequence risk starting to bite
65	50%	50%	Withdrawals beginning
75	40%	60%	Shorter horizon, spending underway

The logic is sound. A fall at 30 gets repaired by ten years of future contributions, while the same fall at 62 has to be repaired by the market alone. The assumption baked in is that you retire in the year printed on the label and start spending immediately, so someone with a pension covering the essentials, or someone planning to work part time until 70, has a different problem from the one that fund is solving.

The 4 percent rule and where it actually came from

The best known number in retirement planning comes from William Bengen’s 1994 study in the Journal of Financial Planning, which tested historical US market data to find the highest first-year withdrawal rate that would have survived a 30 year retirement. Later work by researchers at Trinity University examined success rates across different withdrawal rates and portfolio mixes, and the shorthand that emerged from both was 4 percent.

The mechanics are specific. Withdraw 4 percent of the portfolio in year one, then raise that dollar amount with inflation each year afterwards, without recalculating against the new balance. On $1,000,000 that comes to 0.04 x 1,000,000 = $40,000 in year one, rising with prices from there.

Run it backwards to size a target. To draw $50,000 a year from a portfolio, the same arithmetic implies 50,000 / 0.04 = $1,250,000.

Why the order of the years matters

While you are contributing, a bad year is almost a gift, because the same monthly amount buys more shares, and once you are withdrawing, the same bad year is expensive, because the shares you sell to pay for groceries never come back.

Start retirement with $1,000,000 and a $40,000 first-year withdrawal. Suppose the portfolio falls 25 percent in year one. It drops to $750,000, and after your withdrawal it holds $710,000. Your $40,000 of spending is now 40,000 / 710,000 = 5.6% of what is left, well above the rate the plan assumed, and that share keeps growing every year the balance stays low, because recovering a 25 percent fall takes a 33.3 percent gain even before any withdrawals, which is the arithmetic in measuring portfolio risk and in the drawdown recovery calculator.

Two defences, and most people use both. Hold several years of planned spending in bonds and cash so that shares never have to be sold into a decline, and keep enough flexibility in your spending that a bad year can mean a smaller withdrawal.

What actually goes wrong

Contributions that never rise are the quiet failure. A rate set at 4 percent in your first job does not become adequate because markets did well in the meantime. Raise it with every pay rise. Do it before the extra money reaches your account and starts feeling like yours.

Cashing out a 401(k) when changing jobs is the loud one. It converts decades of compounding into a taxed lump sum that mostly gets spent, and the balance rarely gets rebuilt, while rolling it into an IRA or the new employer’s plan keeps the compounding running.

The third is the one this whole section keeps coming back to. A plan nobody wrote down gets renegotiated in the middle of a bad year, usually at the worst possible moment, and a portfolio that gets abandoned halfway through a decline never earns the returns its owner was counting on. Write the numbers down, revisit them once a year, and let inflation into the conversation while you do, which the real return calculator makes uncomfortably clear.

Start here this week: log into your workplace plan, confirm you are contributing at least enough to capture the full match, and look at what the money is actually invested in, since a surprising number of accounts sit in a default cash fund for years. Then set one annual reminder to rebalance. The portfolio construction quiz will find what is still fuzzy.