Taiwan Strait Tension Index

How the index is built

It follows the rule of the Geopolitical Risk index by Dario Caldara and Matteo Iacoviello, applied to the two presses that face each other across the Strait. Each day, every headline of two national news agencies is read: China News Service, Beijing's state agency, and the Central News Agency, Taiwan's. A headline counts when it names the Strait, the other side or its military, and also a term of threat or of military action.

The index for a month is the share of that month's headlines that count, scaled so that the 2015–2024 average of each agency is 100. The two sides are scaled separately, then averaged, so neither agency outweighs the other because it publishes more.

As in the original, the terms split in two. Threats are warnings, coercion, sanctions, arms sales and war talk. Acts are military activity that took place: exercises, aircraft and ships around Taiwan, missile launches, coast-guard boardings. The monthly file carries both for each side.

What it does not measure

It measures what each government's agency chooses to put in front of its readers, not the military balance. Beijing states its threats politically more often than militarily, so on the China side the condemnation of "Taiwan independence" counts as a threat. Only headlines are read, which makes a single day noisy; the index is meant to be read by the month. A month enters only if at least nine in ten of its days were collected in full, and the numbered episodes are Valtor's annotations.

Not every matching headline is about the Strait. Valtor read a sample of them by hand (292 on the Taiwan side, 120 on the China side). Weighted by each year's number of matches, about 1.9% of the Taiwan side's matches are unrelated to military pressure (a typhoon "threat", a drone show) and another 13.6% concern China's armed forces away from the Strait, on the Indian border or near Japan; that second kind is commonest in the early years, which lifts them relative to later ones. On the China side about 9.8% are unrelated. The monthly file shows the result; the headlines are not published.

How it was checked

The test was fixed before the results were read: 15 dated episodes, from arms sales to the PLA's named exercises. In each, the index for the event month is compared with the average of the three months before. Both sides together rose in 14 of 15; the China side in 13 of 15; the Taiwan side in 14 of 15. The misses are all Taiwanese elections (both sides: January 2016; China side: January 2016 and January 2020; Taiwan side: January 2016), which Beijing's agency mutes and Taiwan's covers as politics rather than threat.

Against Caldara and Iacoviello's index for Taiwan, built from US and British newspapers, the combined series correlates at 0.68 month by month and 0.55 in monthly changes, over 141 months (China side 0.57 and 0.50; Taiwan side 0.74 and 0.56). Against their index for China, which is mostly about other things, it is 0.37 and 0.08: the index tracks the Strait, not China in general.

The word lists are fixed in code; any change rebuilds every month since 2015 and is tested again. The Taiwan side's list was last revised on 14 Oct 2026, after the hand-read audit, to drop noise (Japanese reports of Chinese coast-guard ships off the Senkakus, headlines naming Xi Jinping on other matters, the outlying islands' local news) and to add the defence ministry's daily wording for aircraft and ships around Taiwan. The event test and the correlations were the same before and after.