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arxiv: 2605.25392 · v1 · pith:352ALKWYnew · submitted 2026-05-25 · 💱 q-fin.MF

One Currency, Two Forward Prices: The Onshore-Offshore Renminbi Puzzle

Samuel Drapeau , Peng Luo , Xuan Tao , Tan Wang This is my paper

Pith reviewed 2026-06-29 19:51 UTC · model grok-4.3

classification 💱 q-fin.MF
keywords renminbiCNYCNHforward discrepancyoffshore stresstrading costsspot paritycurrency hedging
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The pith

Random jumps in offshore trading costs explain the persistent CNY-CNH forward discrepancy while preserving spot parity.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper builds a joint equilibrium model of spot and forward trading under transaction costs and segmented supply for the onshore CNY and offshore CNH Renminbi markets. With deterministic costs the model produces a forward differential of the opposite sign from the data even though spot prices stay aligned. Adding random jumps in offshore trading costs reverses the sign of the forward differential without loosening spot parity. The resulting semi-explicit formulas let the authors calibrate the size of the observed discrepancy to the market-implied frequency and magnitude of liquidity stress. Readers care because the setup supplies a concrete mechanism for how hedging demand is priced in partially convertible currencies.

Core claim

In the benchmark case with common constant supply and deterministic costs, spot parity implies a forward differential with the wrong sign relative to the data. Random offshore stress, modeled as a jump in trading costs, overturns this benchmark while preserving tight spot parity. The model yields a semi-explicit representation in the CNY/CNH application and a calibration of the observed forward discrepancy in terms of the market-implied likelihood and severity of offshore liquidity stress.

What carries the argument

A joint equilibrium model of spot and forward trading with transaction costs, segmented supply, and random jumps in offshore trading costs.

If this is right

  • The forward differential admits a semi-explicit expression in the intensity and size of the cost jumps.
  • Spot parity continues to hold tightly even after the jumps are introduced.
  • Observed CNY-CNH prices can be inverted to recover market-implied probabilities and severities of offshore stress.
  • The same framework applies to other partially convertible currencies that maintain deliverable offshore venues.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • Forward markets appear to embed a priced premium for the possibility of sudden offshore liquidity events.
  • The calibration could be checked by comparing implied jump parameters against actual episodes of offshore market tightening.
  • If regulatory or segmentation effects dominate, extending the model to include them would change the extracted stress parameters.

Load-bearing premise

The forward discrepancy is driven primarily by random jumps in offshore trading costs rather than regulatory barriers, investor segmentation, or contract differences.

What would settle it

Market data in which the forward discrepancy vanishes or reverses sign during intervals with no measurable offshore liquidity stress would falsify the jump explanation.

read the original abstract

Partially convertible economies face a market-design problem: trade integration, cross-border investment, and domestic balance-sheet exposure increase the demand for currency hedging before full financial integration is complete. China adopted a distinctive architecture for this problem by fostering a deliverable offshore Renminbi market (CNH) alongside the segmented onshore market (CNY), rather than relying only on non-deliverable forwards. This creates two venues for closely related claims on the same currency. Spot prices are tightly linked, yet CNY and CNH forwards display a persistent and economically large discrepancy. We study that discrepancy in a joint equilibrium model for spot and forward trading with transaction costs and segmented supply. In the benchmark case with common constant supply and deterministic costs, spot parity implies a forward differential with the wrong sign relative to the data. Random offshore stress, modeled as a jump in trading costs, overturns this benchmark while preserving tight spot parity. The model yields a semi-explicit representation in the CNY/CNH application and a calibration of the observed forward discrepancy in terms of the market-implied likelihood and severity of offshore liquidity stress.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

2 major / 0 minor

Summary. The paper develops a joint equilibrium model for spot and forward trading in the segmented CNY and CNH Renminbi markets with transaction costs and segmented supply. In the benchmark case with common constant supply and deterministic costs, spot parity implies a forward differential of the wrong sign relative to the data. The authors introduce random offshore stress modeled as a jump in trading costs, which reverses the sign while preserving tight spot parity. The model yields a semi-explicit representation and calibrates the observed forward discrepancy in terms of the market-implied likelihood and severity of offshore liquidity stress.

Significance. If the mechanism can be shown to operate independently of direct fitting to the target moment, the framework would provide a theoretical account of forward-price discrepancies in partially convertible currencies and could inform market-design choices for hedging demand in emerging economies.

major comments (2)
  1. [Abstract] Abstract: the calibration procedure sets the jump intensity and size so that the market-implied parameters exactly reproduce the average CNY-CNH forward discrepancy. With only one free parameter and a single target moment, the procedure is a direct fit; no additional moments (volatility of the basis, its autocorrelation, or cross-sectional implications) are shown to be matched by the same parameters.
  2. [Abstract] Abstract: the modeling choice that random jumps in offshore trading costs are the primary driver is introduced specifically to reverse the sign of the benchmark forward differential. The manuscript does not report evidence that rules out alternative drivers such as regulatory barriers, investor segmentation, or differences in contract specifications.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for the detailed and constructive report. We address the two major comments point by point below, focusing on the substance of the concerns raised.

read point-by-point responses

  1. Referee: [Abstract] Abstract: the calibration procedure sets the jump intensity and size so that the market-implied parameters exactly reproduce the average CNY-CNH forward discrepancy. With only one free parameter and a single target moment, the procedure is a direct fit; no additional moments (volatility of the basis, its autocorrelation, or cross-sectional implications) are shown to be matched by the same parameters.

    Authors: The calibration is constructed to match the average forward discrepancy by design, with the two parameters (jump intensity and size) chosen to reproduce that single moment and then interpreted as the market-implied likelihood and severity of offshore liquidity stress. The paper's objective is to deliver a joint equilibrium framework that can generate the observed sign reversal while preserving spot parity, rather than to conduct a multi-moment empirical validation. The semi-explicit solution does admit further analysis of volatility or autocorrelation implications, but these are not reported in the current version. We do not view the direct-fit nature of the calibration as a flaw in the theoretical exercise and therefore make no change to the procedure. revision: no

  2. Referee: [Abstract] Abstract: the modeling choice that random jumps in offshore trading costs are the primary driver is introduced specifically to reverse the sign of the benchmark forward differential. The manuscript does not report evidence that rules out alternative drivers such as regulatory barriers, investor segmentation, or differences in contract specifications.

    Authors: The random-jump specification is indeed introduced because the deterministic benchmark produces the wrong sign. The model demonstrates that this single mechanism is sufficient to overturn the benchmark result while keeping spot prices tightly linked. The manuscript does not claim that offshore liquidity stress is the sole driver, nor does it contain evidence that would rule out regulatory barriers, investor segmentation, or contract differences. We present one equilibrium channel consistent with the institutional setting and the data; distinguishing among channels lies outside the scope of the paper. revision: no

Circularity Check

1 steps flagged

Calibration of jump parameters directly reproduces the observed forward discrepancy by construction

specific steps
  1. fitted input called prediction [Abstract]
    "The model yields a semi-explicit representation in the CNY/CNH application and a calibration of the observed forward discrepancy in terms of the market-implied likelihood and severity of offshore liquidity stress."

    The forward discrepancy is the target quantity being explained. Calibrating the jump likelihood and severity parameters to reproduce this exact discrepancy means the semi-explicit representation matches the input data by construction; the procedure does not generate an out-of-sample prediction or match additional moments.

full rationale

The paper first shows that the constant-cost benchmark produces a forward differential of the wrong sign under spot parity. It then introduces a jump process in offshore trading costs specifically to reverse the sign while preserving spot parity. The resulting semi-explicit representation is calibrated so that its market-implied jump intensity and size exactly match the average CNY-CNH forward discrepancy. Because the single target moment determines the free parameters, the central claim that random offshore stress drives the discrepancy reduces to a direct fit rather than an independent test against other moments or alternative mechanisms.

Axiom & Free-Parameter Ledger

1 free parameters · 2 axioms · 1 invented entities

The central claim rests on introducing random offshore liquidity stress as a modeling device whose parameters are calibrated to the observed forward gap; standard equilibrium assumptions and the domain assumption of tight spot parity are also required.

free parameters (1)
  • likelihood and severity of offshore liquidity stress
    Calibrated to reproduce the observed CNY-CNH forward discrepancy
axioms (2)
  • domain assumption Spot prices remain tightly linked across the two markets
    Invoked to preserve spot parity while allowing forward discrepancy
  • standard math Markets clear in joint equilibrium with transaction costs and segmented supply
    Core modeling framework stated in the abstract
invented entities (1)
  • offshore liquidity stress modeled as random jump in trading costs no independent evidence
    purpose: To reverse the sign of the benchmark forward differential
    New device introduced to match data; no independent evidence supplied in abstract

pith-pipeline@v0.9.1-grok · 5729 in / 1519 out tokens · 29554 ms · 2026-06-29T19:51:04.565285+00:00 · methodology

discussion (0)

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Reference graph

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