How Electronic Trading Cut Your Costs to Nearly Zero
Decades ago, buying 100 shares meant a phone call to a broker who relayed an order to a trading floor and charged a fixed commission regardless of size. Today the same trade executes in milliseconds through computer networks for a commission close to nothing, which is why retail investing became genuinely affordable at all.
The core principle: automation replaces intermediaries
Electronic trading replaced human intermediaries, floor brokers relaying orders by voice, specialists standing at a fixed post matching buyers with sellers, with computer systems that match buy and sell orders automatically at extraordinary speed. This matters for two distinct reasons: execution speed and cost. When order matching is automated, the marginal cost of executing one more trade falls toward the cost of computing power, essentially negligible, rather than the cost of paying a human's time and attention for each individual transaction.
The shift did not happen overnight. It unfolded gradually across decades as exchanges digitized their order books, regulators mandated more competitive market structures, and new electronic venues emerged to compete directly with traditional floor-based exchanges for order flow, each new source of competition pushing costs down further for the investors placing trades.
An earlier generation of investors experienced the trading process very differently from today's near-instant app-based execution. Placing an order often meant calling a broker directly, who would relay the instruction by phone or telex to a representative physically present on an exchange floor, where the order was matched by voice negotiation with a counterparty, and confirmation of the completed trade could take minutes rather than the fraction of a second an order takes to fill today. That older process was not merely slower, it was also considerably more expensive to run, since it required paying for a chain of human intermediaries at every step between an investor's phone call and a completed trade, each of whom needed to be compensated regardless of how small the underlying order actually was.
What actually changed
Three linked developments drove the shift. First, electronic order matching replaced manual floor-based matching with algorithms that pair compatible buy and sell orders continuously, without needing a human specialist to hold the order book. Second, regulatory changes over the decades pushed toward a more fragmented, more competitive market structure, allowing multiple trading venues to compete for the same order flow rather than concentrating trading in a single exchange floor. Third, broker competition intensified as online brokerages proliferated, and the marginal cost savings from automation eventually got passed through to customers in the form of dramatically lower, and eventually zero, stated commissions on many types of trades.
Alongside falling commissions, electronic trading also compressed the bid-ask spread, the gap between what buyers offer and what sellers ask, because faster, automated matching lets many participants compete simultaneously to fill an order rather than relying on a single specialist's quoted price. More competition to provide liquidity has historically meant a tighter spread for the investor placing the trade.
Electronic trading also enabled an entirely new category of market participant, the high-frequency and algorithmic trading firm, which uses automated systems to post and adjust quotes across thousands of securities continuously throughout the trading day, often holding positions for mere seconds or fractions of a second. These firms have become significant liquidity providers in many markets, and the competition among them is part of why spreads on liquid securities have compressed so substantially, though their presence has also drawn scrutiny over whether their speed advantage extracts value from slower participants during specific, narrow trading situations, a genuinely contested question in market structure research that does not have a single settled answer.
The math: what old commissions actually cost you
Worked example one: commissions as a percentage drag. Consider a retail trade in an earlier era of investing, when a typical commission might run 75 dollars per trade regardless of size. On a 2,000 dollar investment, that commission alone represents 75 / 2,000 = 3.75 percent, lost before the position has moved at all. If markets have historically returned somewhere in the range of 7 to 10 percent a year before costs, that single commission has effectively consumed close to half a year's worth of expected return on day one. By contrast, a modern trade at a competitive online broker charging 0 dollars commission starts with zero drag from that line item, meaning the full amount of any subsequent gain accrues to the investor rather than being split with an intermediary before the trade even begins.
Worked example two: spread compression. A stock once traded with a 25 cent spread on a 30 dollar share price, or 0.25 / 30 = 0.83 percent of the trade value. The same stock today, under electronic, competitive market making, might trade with a 1 cent spread on a comparable price, or 0.01 / 30 = 0.03 percent, a reduction of more than 96 percent in the spread's proportional cost. For an investor who trades in and out of a position 20 times over a career, the older spread would have cost roughly 20 x 0.83 percent = 16.6 percent of cumulative trade value in spread alone, versus roughly 20 x 0.03 percent = 0.6 percent under modern conditions, a difference that compounds into real, retained wealth over decades of investing.
Worked example three: the combined effect over a career. Consider an investor who makes 40 trades over a 30-year investing career, each averaging 5,000 dollars. Under the older cost structure, a 75 dollar commission plus a wider average spread cost of roughly 0.5 percent, or 25 dollars, per trade totals 100 dollars per trade, or 40 x 100 = 4,000 dollars over the career purely in trading friction. Under a modern cost structure, zero commission plus a tighter average spread cost of roughly 0.05 percent, or 2.50 dollars, per trade totals just 40 x 2.50 = 100 dollars over the same career, a reduction of 97.5 percent in cumulative trading friction. That 3,900 dollar difference, left invested rather than paid out in fees, would itself have compounded meaningfully over the following decades.
What the historical record shows
The historical trend in trading costs over recent decades is one of the more unambiguous, well-documented improvements in market structure for ordinary investors: commissions, spreads, and overall transaction costs for liquid, widely traded securities have fallen substantially and persistently as electronic trading and competition among venues and brokers increased. Alongside that genuine improvement, research on individual investor behavior has consistently found a less flattering pattern: as the friction of trading dropped, average trading frequency among retail investors rose, and higher-frequency traders have repeatedly been shown, across multiple independent studies using brokerage account data, to earn lower net returns on average than more patient, less active investors, largely attributable to poor timing decisions rather than to explicit trading costs alone, which by this point are quite low for most ordinary trades.
This finding has shown up with notable consistency across studies using different populations, time periods, and account types, which strengthens the case that it reflects a genuine behavioral pattern rather than an artifact of any single dataset. The most frequently traded accounts in these studies have tended to underperform not because any individual trade was necessarily a poor decision, but because a higher volume of decisions creates more opportunities for the small, systematic timing errors that behavioral research has documented in individual investors, buying after a run-up, selling after a decline, chasing recent news, each error small on its own but compounding across dozens or hundreds of trades into a measurable gap versus a comparably invested but far less active portfolio.
How this changes real investor behavior
For a long-term, buy-and-hold investor building a diversified portfolio, the practical benefit of electronic trading is straightforward and almost entirely positive: rebalancing, dollar-cost averaging into index funds, and making occasional adjustments now cost a small fraction of what they once did, removing a real barrier that used to discourage disciplined, regular investing. The risk this same low friction introduces is behavioral rather than mechanical: when trading costs nothing to think about, some investors trade far more often than the evidence supports as beneficial, mistaking frequent activity for progress toward their goals. The lesson is not to distrust electronic trading itself, but to recognize that the removal of a cost barrier does not remove the underlying behavioral discipline required to invest well.
Busy, high-earning professionals often benefit specifically from leaning into this low-friction environment for automation rather than for activity: setting up recurring automatic investments that execute on a fixed schedule regardless of market headlines captures the cost benefits of electronic trading, near-zero commission, tight spreads on liquid funds, without introducing the behavioral risk of frequent, discretionary trading decisions squeezed in around a demanding work schedule. This is arguably the single most practical way a modern investor can benefit from decades of market structure improvement while sidestepping the pitfall that improvement also created.
Actionable breakdown
- Take advantage of low costs deliberately:
- Use commission-free rebalancing to stay on target.
- Automate regular contributions since the friction is now minimal.
- Stay alert to remaining, hidden costs:
- Check whether your broker sells order flow to market makers.
- Watch the bid-ask spread on thinly traded securities regardless of commission.
- Guard against the behavioral trap:
- Set a rule for how often you will actually trade.
- Treat zero commission as removing a barrier, not as an invitation to trade more.
Common pitfalls
A common misconception is treating a zero-commission broker as having literally no cost, when payment for order flow and execution quality differences can still create a small implicit cost on every trade. A second pitfall is trading far more frequently simply because the friction is gone, a behavioral shift that research on investor returns has repeatedly linked to worse, not better, long-run outcomes. A third is assuming spreads are equally tight across all securities, when thinly traded stocks and niche funds can still carry meaningfully wider spreads even in a fully electronic market. A fourth is confusing execution speed with execution quality, since a trade that fills instantly is not automatically a trade that filled at the best available price. A fifth is failing to automate recurring contributions once trading costs stop being a meaningful obstacle, leaving genuine convenience gains on the table out of simple habit.
The bottom line
Electronic trading made investing dramatically cheaper and faster, but those savings only compound in your favor if you resist the temptation to trade more simply because you now can, and instead put the freed-up friction toward automated, disciplined contributions that do the compounding work quietly, in the background, without requiring a single additional click, decision, or moment of willpower on a busy week already full of competing demands.
Related reading: how markets work, how securities are traded, trading costs, new trading strategies.