--- title: "Congress's press releases doubled their em dashes. Two years after ChatGPT." url: https://deadwritingtheory.com/cases/the-em-dash-goes-to-congress/ summary: "Unspaced em dashes in 146,239 US congressional press releases more than doubled in 2025, within the same offices. But nothing moved when ChatGPT arrived. A preregistered preprint." published: 2026-10-18 updated: 2026-10-18 author: "Jack Stovell" publisher: "Adapt Progress Evolve Limited" language: en-GB --- # Congress's press releases doubled their em dashes. Two years after ChatGPT. Unspaced em dashes in 146,239 US congressional press releases more than doubled in 2025, within the same offices. But nothing moved when ChatGPT arrived. A preregistered preprint. **Case No. DWT-015: The em dash goes to Congress.** Split verdict. Filed 18 October 2026. - **The question:** Did unspaced em dashes become more common in US congressional press releases after ChatGPT's release, and when? - **The sample:** 146,239 press releases from 480 House and Senate offices, 2021 to 2025, from the open congress-press dataset; unspaced em dashes in prose counted per 1,000 characters after stripping the dateline, against the preregistered ChatGPT cut-off of 30 November 2022 - **The study:** Przemysław Czuma (Polish Association for Artificial Intelligence in Medicine), "The em-dash em-beds in Congress: A population-level rise in em-dash frequency in U.S. congressional press releases at the dawn of the large-language-model era, 2021-2025", arXiv preprint (preregistered on OSF), 2026. https://arxiv.org/abs/2608.05889 - **Whose study:** Third-party study. Not our study. Entered into evidence from Przemysław Czuma, Polish Association for Artificial Intelligence in Medicine. - **Peer review:** Preprint, not yet peer reviewed ## Findings of fact 1. Unspaced em dash density stayed within 0.10 to 0.12 per 1,000 characters from 2021 through 2024, then rose to 0.217 in 2025, more than twice the four-year baseline. 2. The share of releases with at least one such em dash rose from about 13% to 24.8%. 3. Of 262 offices with at least 10 releases in both periods, 75.6% increased their em dash use. Hyphens stayed near 2.7 per 1,000 characters. 4. No upward step at the ChatGPT cut-off: about 97% of the total increase occurs in 2025. ## Caveats for the jury - A single-author preprint, not yet peer reviewed. - The study's own validation gate failed (leftover datelines above the preregistered 2% threshold), so "the full preregistered decision rule was not met" and the author calls the LLM reading exploratory. - Almost all of the rise came in 2025, the year a new Congress and a new administration began. The author says the corpus "cannot fully separate" model use from staff turnover. - It measures one mark becoming more common, not who wrote any release: "the em-dash is not a detector". One country, one genre. ## The court reporter's account Right, the court is in session. The defendant is a punctuation mark, the em dash, and the charge is that it spread through congressional press releases once language models arrived. I'm only the court reporter, so I take no side. I just write down what was said. The evidence comes from a single-author preprint by Przemysław Czuma, of the Polish Association for Artificial Intelligence in Medicine, titled "The em-dash em-beds in Congress". It's from August 2026, it isn't peer reviewed, but it was preregistered on the Open Science Framework before any confirmatory result was calculated. Fair point in its favour. Why press releases? Well, AP style puts spaces around a dash, so the unspaced form written straight between two words is unusual in this genre. Low human baseline. Member offices also publish without an outside typesetter, so their own typography survives. The study took 146,239 releases from 480 House and Senate offices, 2021 to 2025, and counted unspaced em dashes per 1,000 characters of cleaned text, after stripping the "CITY, ST" dateline. The preregistered cut-off was ChatGPT's public release on 30 November 2022. The uncertainty was adjusted for repeated releases from the same office, and three placebo cut-offs were tested. The prosecution goes first. Density sat between 0.10 and 0.12 from 2021 through 2024, then rose to 0.217 in 2025, more than twice the four-year baseline. The share of releases with at least one such em dash went from about 13% to 24.8%. The primary ratio was 1.55 (95% CI 1.28 to 1.93), just above the preregistered 1.5 times threshold. Of 262 offices with enough releases in both periods, 75.6% increased their use, and a closed panel of 224 offices went from 0.103 in 2024 to 0.192 in 2025. Same offices, changed style. Dropping the 24 busiest offices left the ratio at 1.66, so a few prolific offices aren't carrying it. Hyphens stayed near 2.7 per 1,000 characters, the en dash stayed flat, and the placebo cut-offs showed no increase. Now the defence, and it's a good one. Nothing happened when ChatGPT arrived. Density was 0.1047 in 2023 and 0.1157 in 2024. The time-series model found no upward step at the cut-off, "if anything a temporary dip". About 97% of the increase falls in 2025. The author writes that the change "appeared substantially later than the simplest 'ChatGPT released, writing changed immediately' story would predict." Then there's January 2025: a new Congress, a new administration, a change in the Senate majority. Staff turnover could shift style without any model. The rise was about 1.9 times for both Democrats and Republicans within continuing offices, which weighs against a simple party story, but the author says the corpus "cannot fully separate" the two. The quality gate also failed. The leftover dateline rate was above the preregistered 2% threshold, so "the full preregistered decision rule was not met". Hence the LLM reading is "exploratory rather than confirmatory". Averaging yearly figures instead of pooling them gives 1.43 times, which fails the thresholds. I should say plainly what this measures: one mark becoming more common, its prevalence. It doesn't say who wrote any release, and it doesn't show that LLMs caused anything. The author agrees: "the em-dash is not a detector", and the study "does not support a causal claim". One country, one genre. So the mark really did more than double, broadly and within the same offices. But it didn't move when ChatGPT arrived, the jump coincides with a new Congress, and the author calls the explanation exploratory. Verdict: split. ## The exhibits entered in this case ### For the prosecution - **Exhibit P-18**: Em dashes in Congress's press releases more than doubled in 2025. **0.217** unspaced em dashes per 1,000 characters in 2025, up from 0.10 to 0.12 in 2021 to 2024. 146,239 releases from 480 offices. 75.6% of 262 offices increased their use; hyphens stayed near 2.7 per 1,000, so it was not conversion. Releases with one rose from about 13% to 24.8%. ### For the defence - **Exhibit D-19**: Nothing happened when ChatGPT arrived. **97%** of the rise came in 2025, more than two years after ChatGPT's release. About 97%. No upward step at the cut-off: 0.1047 per 1,000 characters in 2023, 0.1157 in 2024. 2025 also brought a new Congress, and the author calls the LLM reading exploratory. ## The finding Unspaced em dashes in 146,239 US congressional press releases more than doubled in 2025, within the same offices. But nothing moved when ChatGPT arrived. A preregistered preprint. ## Related - [The words changed. The sentences did not.](https://deadwritingtheory.com/cases/did-chatgpt-change-how-companies-write/) - [Not an invention. An inheritance.](https://deadwritingtheory.com/cases/where-did-ai-isms-come-from/) - [The machine's words spread through medicine, measured without a detector.](https://deadwritingtheory.com/cases/the-delve-study-done-properly/) ## Sources - [Czuma, "The em-dash em-beds in Congress: A population-level rise in em-dash frequency in U.S. congressional press releases at the dawn of the large-language-model era, 2021-2025", arXiv preprint (preregistered on OSF), 2026 (the original study)](https://arxiv.org/abs/2608.05889) - [The study's preregistration on the Open Science Framework](https://doi.org/10.17605/OSF.IO/U5NEY) - [congress-press, the open dataset of congressional press releases (MIT licence)](https://github.com/dwillis/congress-press) ## Questions people ask ### Do US Congress press releases use more em dashes since AI? Yes, in 2025. Czuma (arXiv preprint, 2026) found unspaced em dashes in 146,239 congressional press releases stayed within 0.10 to 0.12 per 1,000 characters from 2021 through 2024, then rose to 0.217 in 2025. ### Did it start when ChatGPT came out? No. The study found no upward step at ChatGPT's release on 30 November 2022. About 97% of the increase came in 2025, more than two years later. ### Does this prove congressional staff use ChatGPT? No. The author is explicit that "the em-dash is not a detector" and that the study "does not support a causal claim". 2025 also brought a new Congress, which could change house style on its own. ### Is this peer reviewed? Not yet. It is a single-author arXiv preprint from August 2026, preregistered on the Open Science Framework. Its own validation gate failed, so the author calls the LLM reading exploratory.