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  "identification": {
   "estimand": "Effect of TBA eligibility and of parallel TBA trading volume on SP trading costs; dealer hedge ratios of SP inventory with TBA trades",
   "strategy": "Trading-cost regressions on consecutive trades; regression discontinuity at the 1.05 LTV eligibility threshold; propensity score matching on the estimated probability of eligibility; predictable dollar-roll volume before settlement used as exogenous variation in TBA volume; dealer-level inventory regressions",
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    "claim": "TBA-eligible SPs have significantly lower trading costs than ineligible SPs",
    "evidence_type": "table",
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   },
   {
    "claim": "Trading costs jump when the LTV eligibility threshold is crossed, supporting an effect of eligibility itself",
    "evidence_type": "table",
    "evidence_ref": "Table III; Figure 3"
   },
   {
    "claim": "Eligibility lowers costs after matching on estimated eligibility probability",
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   },
   {
    "claim": "SP trading costs fall on days of predictably high TBA dollar roll volume",
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   },
   {
    "claim": "Dealers hedge SP inventory changes with offsetting TBA trades, less so for ineligible SPs",
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    "evidence_ref": "Table VII"
   },
   {
    "claim": "TBA trades hedge price changes of eligible SPs better than those of ineligible SPs",
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    "evidence_ref": "Table VIII"
   },
   {
    "claim": "Prearranged trades are more common for hard-to-hedge SPs",
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    "evidence_ref": "Table IX"
   }
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  "structural_summary": "The paper opens with the puzzle of high liquidity in a market of unique securities and proposes three channels through which TBA trading creates liquidity. It positions itself against prior trading-cost studies and previews the hedging result and a policy implication for bond markets. After institutional background and data sections, the results proceed in steps: trading-cost benchmarks, then the causal effect of eligibility using RD and matching, then spillovers using predictable dollar-roll volume, then evidence on dealer hedging and prearranged trades. The conclusion restates findings and proposes forward markets for municipal and corporate bonds.",
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   "OTC liquidity",
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