Dollar-Cost Averaging Through Every Paycheck

In March 2020, a GS-12 at a regional VA office, I'll call her Dana, opened her TSP account on her lunch break and felt her stomach drop. Her balance had fallen by almost a third in a few weeks. Her contribution was set at 10% of pay, and a coworker had just told her to "turn it off until things settle down."

Her cursor hovered over the contribution election screen for a long time.

She left it alone. Over the next several months, every paycheck bought shares at prices far below where they'd been in February. She didn't think of it as a clever move. She just didn't do anything. That, as it turns out, is the strategy.

What actually happens when you contribute every pay period

Dollar-cost averaging means investing a fixed amount on a regular schedule, regardless of what the market is doing. If you contribute to the TSP through payroll, you're already doing it. Each pay period, your contribution is converted into shares of whatever funds you've chosen, at that day's share price. When prices are high, your dollars buy fewer shares. When prices are low, they buy more.

Here's a simple example. Say you put $400 per pay period into a fund, and over five pay periods the share price moves like this:

Pay period	Share price	Shares bought
1	$50	8
2	$40	10
3	$25	16
4	$40	10
5	$50	8

You invested $2,000 and own 52 shares. Your average cost is about $38.46 per share, below the simple average of the five prices ($41). The price ended exactly where it started, at $50, yet your 52 shares are worth $2,600. You're up $600 on a market that, by the price chart alone, went nowhere.

The dip in period three did the work. Cheap shares are the reward for continuing to buy during the stretch when continuing feels worst.

What dollar-cost averaging does not do

Let's be honest about the limits, because some writers oversell this.

It doesn't guarantee a profit. If prices fall and never recover, you'll lose money. It doesn't beat the market. And if you're sitting on a lump sum, say an inheritance or a rollover from an old employer plan, the research tends to show that investing it all at once beats spreading it out roughly two-thirds of the time, simply because markets rise more often than they fall. Vanguard and others have published studies on this, and they're worth reading.

But that's a different question from the one most of us face. Dana didn't have a lump sum. She had a paycheck. You can't invest money you haven't earned yet, so for a working employee, the choice isn't "lump sum versus DCA." It's "invest each paycheck as it arrives, or wait for a better moment that never announces itself."

Paycheck investing is DCA by necessity. The strategy's real value is what it does to your behavior.

The behavioral edge

A fixed, automatic contribution takes you out of the decision loop. You don't have to guess whether this is the bottom, or the top, or whether the news cycle is about to get worse. Those guesses are expensive. People who try to time contributions tend to pause after drops and resume after recoveries, which is the exact reverse of what helps.

Automation also protects your match. FERS employees receive an automatic 1% agency contribution plus matching on the next 4% of pay they put in, which adds up to a 5% employer contribution if you contribute at least 5%. Members under the Blended Retirement System have a similar structure. Stopping contributions in a downturn means walking away from that match during the very months when your own dollars are buying at a discount. Check tsp.gov for current match rules and contribution limits, since the dollar limits adjust most years.

Putting it to work in the TSP

A few practical moves that fit the approach:

• Pick a percentage, then raise it. Many federal employees set a contribution once and never revisit it. Tie increases to raises. Step increases, within-grade bumps, and annual pay adjustments are natural moments to move from 8% to 9% or 10% before the extra money reaches your checking account.
• Use the full year's pay periods. If you're aiming to hit the annual elective deferral limit, divide it by your number of pay periods rather than front-loading. Front-loading can work, but if you hit the limit early, some agencies' matching rules can leave you short of the full match. Verify how your payroll office handles this.
• Keep your allocation steady. Whether you're in the L Funds or a mix of C, S, I, F, and G, resist the urge to redirect future contributions to the G Fund after a scary drop. That locks in the fear and misses the recovery.

The same idea in an IRA

An IRA doesn't run through payroll, so you have to build the automation yourself. Most brokerages let you schedule recurring transfers from checking into a traditional or Roth IRA, with automatic purchases of the funds you've picked.

The simplest method is to take the annual contribution limit, which the IRS adjusts periodically (see irs.gov for the current figure), and divide it by 12 or 26. Purely as an illustration, if the limit were $7,000, that works out to roughly $270 per biweekly pay period or about $583 per month. Set it up so the transfer lands right after payday, and the money is invested before you can find something else to do with it.

Roth eligibility has income phaseouts that also change yearly, so confirm those on irs.gov before assuming you can contribute directly.

When the logic flips

Dollar-cost averaging works in your favor during the accumulation years. Near and in retirement, the mirror image applies. If you're withdrawing a fixed dollar amount each month from a portfolio that's falling, you're selling more shares at lower prices, and that can do lasting damage. This is often called sequence-of-returns risk.

That's why people within five to ten years of retirement often keep a cushion in lower-volatility holdings like the G or F Fund, or hold some cash. Your withdrawal plan should be built with a bad first few years in mind. A TSP or IRA account isn't a regular paycheck, and it shouldn't be treated like a purely accumulating one forever.

Back to Dana

By the end of 2021, her balance had passed its February 2020 level and kept climbing. The shares she bought in spring 2020 carried much of that gain. Had she paused for six months, she'd have missed the cheapest shares she was likely to see in a decade.

She didn't outsmart anyone. She just kept the contribution running, which is less exciting than a strategy and more dependable. Look at your own election this week. If it's been the same percentage for three years, that's the place to start.