APN Codex 21600:
Market Sentiment & Behavioural Analysis

The $ICR_t$ functions as a leading indicator for sovereign macroprudential intervention by quantifying the proportional divergence between speculative and utility-driven capital within total mortgage origination. The series peak of +1.8347σ in Q2 2015 preceded APRA's 10 per cent annual investor credit growth benchmark by a single quarter. The Q4 2017 return to negative territory (−0.2178σ) followed APRA's 30 per cent interest-only lending cap, confirming the node's diagnostic utility across two complete regulatory cycles.

The terminal reading of +0.8307σ at Q4 2025 reflects an investor cohort that re-accelerated origination throughout 2024 and 2025. Investor lending expanded 31.8 per cent year-on-year in Q4 2025 against owner-occupier growth of 18.6 per cent, confirming the structural asymmetry that catalysed APRA's February 2026 $DTI \ge 6x$ constraint. The 2.83× differential in high-DTI origination between cohorts empirically validates that investor participation is governed by sequential equity extraction rather than baseline income serviceability.

The $BMM_t$ captures the compounding interaction between price velocity and transaction velocity. A positive product of two positive vectors confirms expansionary momentum; a positive product of two negative vectors — as observed in Q3 2022 — identifies a supply-withdrawal dynamic rather than a market correction. During Q3 2022, mean dwelling prices fell $36,800 (−3.33% QoQ) while transaction velocity contracted 11.35% QoQ. The $BMM_t$ nevertheless registered +1.227σ, correctly diagnosing that incumbent asset holders withdrew inventory rather than accepting price discounts under rising serviceability constraints.

The terminal reading of +0.847σ reflects simultaneous price and transaction acceleration into Q4 2025, with $\Delta P_t$ at +2.74% QoQ and $\Delta TV_t$ at +10.63% QoQ — both vectors positive and above their respective 15-year means. This configuration is structurally consistent with the pre-constraint environment in which the investor cohort accelerated origination ahead of the February 2026 APRA $DTI \ge 6x$ activation.

The $AVRS_t$ integrates rolling price standard deviation, absolute price velocity, and inverse transactional liquidity into a single standardised risk signal. The ratified 8-quarter rolling window produces an effective baseline of N=50 (Q3 2013 – Q4 2025). The nominal 15-year baseline (Q1 2011 – Q4 2025) remains the fixed reference frame for all contextual macroeconomic interpretation.

The Phase III Structural Volatility Event (Q4 2020 – Q3 2022) is the defining feature of the series. The $AVRS_t$ reached +4.2119σ at Q4 2021 — the only breach of +4.0σ recorded — driven by the simultaneous expansion of $\sigma_{P,8}$ to 78.74 and a $dP_t$ of +51.1. The terminal reading of +0.1073σ constitutes the earliest empirical signal of a renewed volatility build. The $\sigma_{P,8}$ component remains elevated at 34.83 relative to its Phase I range, confirming residual structural momentum in the rolling volatility window despite the post-event normalisation trajectory.

The three-series architecture of Node 21640 is designed to expose the structural divergence between declared market psychology and revealed transactional behaviour. Both the $CSI_t$ and $BSI_t$ are ingested via the OECD first-order normalisation layer, which applies Hodrick-Prescott filtering, seasonal adjustment, and amplitude rescaling before APN Z-Score standardisation is applied. This ensures declared sentiment inputs are cleansed of transient anomalies prior to comparison with observed transaction volumes.

The seven-quarter $CSI_t$ suppression epoch (Q1 2023 – Q3 2024, ranging from −2.0911σ to −1.5476σ) is the defining feature of the recent baseline. Despite this sustained pessimism, $Z_{OO\_TV}$ remained positive for much of the period, confirming the non-discretionary transaction floor thesis: owner-occupier activity was sustained by demographic necessity and sequential equity deployment rather than declared consumer optimism. The terminal $SDS_t$ of −0.9007 at Q4 2025 reflects that $Z_{OO\_TV}$ (+0.9649σ) continues to run materially ahead of the recovered sentiment composite, consistent with the structural pattern established throughout the suppression epoch.