The N/A Cell in Swimming Data: The Discipline of an Honest Analyst

At two in the morning in Saigon, my spreadsheet had nineteen rows and not a single number in any of them. The 50m split column was empty. The reaction-time column was empty. The stroke-rate column was empty. I stared at that hollow frame for about four minutes, then typed one line into the summary cell: “N/A — insufficient information to assess.”

My old editor called back to ask whether I was ill. I was not. I had just done the hardest thing sixteen years of watching swimming has taught me: to leave an empty cell alone.

Swimming is a sport measured in hundredths of a second that publishes exactly one number to the public on the scoreboard. Football has xG, PPDA, pass maps. Basketball has tracking for every footfall. Athletics has 100m splits and wind readings. Swimming has a results sheet printed poolside: name, time, and sometimes a 50m split.

Since 2026, when I started as a swimming reporter at Thanh Nien Bao, I have been used to that sheet. Reaction time almost never appears. Stroke rate, distance per stroke, the depth of the underwater phase off the start — absolutely not. They print one number and treat it as the whole story. The whole story sits somewhere else.

A 200m freestyle race contains eight turns, one start, one finish, and roughly three hundred stroke cycles. The final number is the sum of all of it, yet it says nothing about any of it.

So I built a nine-dimension analytical framework for swimming and kept it quiet for years. Space does not allow the full list here, but the point is structural: three of those nine dimensions can be read directly from a results sheet. The other six cannot.

The technical dimension is the most expensive and the most frequently left blank. A world-class swimmer's reaction time typically falls between 0.6 and 0.7 seconds. In a 50m race, that gap is worth several places. You will not find it on the scoreboard. Reaction time is a confession, not a statistic — it tells you how a swimmer had prepared in the ten seconds before the whistle.

The 15-metre rule is another example. Swimmers may travel underwater for a maximum of 15 metres after the start and after each turn. In a 25m pool, that means most of the race happens beneath the surface. Yet no meet publishes how far its athletes actually travel underwater, which turns short-course versus long-course comparison into decorated guesswork.

Then there is split structure. A race can be faster on the front half or the back half. Without split data you cannot separate a swimmer who paced evenly from one who flew out and died. Two athletes can finish within the same hundredth and carry entirely different stories.

The performance dimension needs era context. In 2026-2026, when high-tech racing suits were still legal, world records fell in waves within months. Placing a 2026 mark beside a 2026 mark without mentioning the suit is a methodological error, not a numerical one.

The athlete-career dimension is the one the public skips most, and the one that produces the most false conclusions. For female swimmers, the puberty barrier is the single largest variable of an entire career. Some athletes peak at 14 and then spend three years adapting to a different body. Read only the results and you will write that she is finished — when she is actually mid-way through a biological process no results sheet records.

Nguyen Thi Anh Vien is the case where I had to keep the cell empty for a long time. At Rio 2026 she finished ninth in the 400m individual medley heats, one place short of the final. I had enough data to write a tribute and enough to write a lament. I did not have enough to explain why. Explaining why required the 50m splits of all eight swimmers ahead of her, and I did not have them.

The competition-system dimension is simpler but rarely read. World Aquatics Olympic standards come in two tiers: an A standard for direct qualification and a B standard for quota-based consideration. Hitting a B standard does not guarantee a Games berth. A beautiful time at a national meet can mean nothing at selection level. Nguyen Huy Hoang won silver in the 1500m freestyle at the 2026 Asian Games — a verifiable fact. What that fact does not tell you is which doors it opened or closed four years later.

This is where I break with most of the sports media industry. Swimming is not so data-poor that analysis is impossible. Swimming is so data-poor that people are forced to invent stories to fill the gaps.

“Prodigy.” “Rising above herself.” “National spirit.” “Finding form.” Those phrases describe nothing measurable; they simply occupy the empty cell nobody wants to leave alone.

Numbers do not lie, but they do hide things. When a number hides too much, a writer has two options: write “insufficient information,” or write a story. The second option always pays faster.

I also distrust causal conclusions drawn from a single variable. A swimmer who improves after changing coaches may be coming out of the puberty barrier, may have cut her event load, may be racing in a different pool, may have been reclassified into a different age group. Four explanations, one observable variable. Correlation is not causation — a cliché this industry breaches every week.

The signal I am watching over the next few seasons is specific: whether any meet begins publishing reaction times, 50m splits and stroke counts for entire races, in open form. If that happens, the swimming analytics market will be repriced within eighteen months.

Until then, the advantage belongs to whoever can hold an empty cell without filling it.