USDD backing reconciliation: supply by chain, collateral mix and TVL-drop attribution

The TRX price move explains at most about 13% of the decline. At least about 87% is a fall in collateral quantity, or a tracker change, concentrated on Oct 11-12. I could not identify the specific withdrawals or liquidations. (1) Data: DefiLlama USDD Tron TVL daily points already cited (Oct 9 $1,261.2M, Oct 10 $1,289.7M, Oct 11 $1,271.1M, Oct 12 $1,182.3M, Oct 13 $1,174.3M). TRX daily price (aggregate market data, 00:00 UTC): Oct 9 $0.33202, Oct 10 $0.33080, Oct 11 $0.33068, Oct 12 $0.33154, Oct 13 $0.32907. (2) Split, Oct 9 to Oct 13: TVL -6.89% (-$86.9M) while TRX fell only -0.89%. Even if 100% of TVL were TRX-priced, the price effect is at most -$11.2M (about 13% of the drop). With the last available mix (about 92% WTRX plus sTRX, May 2026) it is about -$10.3M. So at least -$75.7M, or 6.0 of the 6.9 points, is a quantity effect. In TRX-equivalent terms, TVL divided by price fell from about 3.80B to about 3.57B. (3) Timing: almost all of it fell on Oct 11 to 12. TVL -$88.8M (-6.99%) on a day when TRX rose +0.26%, so that step is entirely non-price: withdrawals, liquidations, or a DefiLlama methodology or adapter change. (4) Not achieved: DefiLlama's per-token unit breakdown for these dates was not retrievable (the API response truncates at May 2026), and I have no Tron transfer or contract access, so the quantity drop is not attributed to specific vaults, users or liquidations. A tracker reclassification on Oct 12 cannot be ruled out. Note that DefiLlama's Tron series reads about $1,195.9M at 2026-10-16 12:32 UTC, partly recovering. Not a trade signal.

The token supply read directly from the chains sums to 1,561.41M USDD. That is 248.6M below the official 1.81B and 28.4M above DefiLlama's 1.533B. Most of the gap to the official figure is explained by what is counted: the official per-chain figures match each chain's internal CDP debt (Vat.debt), not its token totalSupply. (1) Token totalSupply, contracts from official docs (docs.usdd.io/developers/deployment-addresses): Tron TXDk8mbtRbXeYuMNS83CfKPaYYT8XWv9Hz = 1,306,535,414.92 (Tronscan API, read about 14:35 UTC Oct 16). Ethereum 0x4f8e5de400de08b164e7421b3ee387f461becd1a = 252,317,595.40 (eth_call totalSupply, block 26205731, 14:35:47 UTC). BNB Chain 0x45e51bc23d592eb2dba86da3985299f7895d66ba = 2,557,434.73 (block 127995395, 14:35:46 UTC). All 18 decimals. Legacy USDDOLD on Tron (TPYmHEhy5n8TCEfYGqW2rPxsghSfzghPDn) adds 7,169,445.41 and is excluded from the sum. (2) Double-counting: each chain has its own Vat, USDD Join and PSM in the official deployment list, so supply is issued natively per chain, not lock-and-mint. On this evidence the three supplies are additive. Caveat: none of the top 20 Tron holders is tagged as a bridge custodian, but most of them are unlabeled, so a bridge lock is not fully ruled out. The largest holder is jUSDD on JustLend (427.0M). That is a lending deposit, not double issuance. (3) Gap to the official 1.81B: on Ethereum, Vat.debt() at 0xff77f620...097f = 460,919,800.69 USDD (block 26205734). That matches the reported 'over 450M' but is 208.6M above ERC-20 supply. On BNB Chain, the Vat address shown in the docs is in Tron format. The Vat address read from USDD Join.vat() is 0x41f1402ab4d900115d1f16a14a3cf4bdf2f2705c, and its debt() = 21,720,404.93 (block 127995552). That matches 'over 21M' but is 19.16M above supply. Together these explain 227.8M of the 248.6M gap. The roughly 20.8M remainder would be Tron Vat debt above Tron token supply. I could not read the Tron Vat, so this part is an inference, not verified. The excess debt is minted USDD that has not been converted to tokens through the USDD Join, held inside the Vat (for example by protocol modules). Vat.vice (unbacked system debt): Ethereum 12,769,215.13, BNB Chain 932,066.82. (4) Gap to DefiLlama's 1.533B (Oct 13 read; explorer reads are Oct 16): Ethereum matches (252.15M vs 252.32M). Tron is 42.5M higher on-chain (1,306.5M vs 1,264M). BNB Chain is 13.75M lower on-chain (2.56M vs 16.31M). The Tron and BNB differences are unexplained: they could be DefiLlama excluding protocol-held balances, timing differences, or a different BNB contract. Not a trade signal.