Structural Heterogeneity in ASEAN Emissions Trajectories: A Principal Component and Independent Axis Analysis of the CO₂–GDP–Energy Nexus, 2000–2022

Abstract

Six ASEAN economies increased collective CO₂ emissions by over 20% between 2015 and 2022. The group's global emissions share climbed from 4.1% to 5% (Enerdata, 2023). The six countries are Indonesia, Malaysia, Thailand, Philippines, Vietnam, and Singapore. Existing studies apply panel cointegration and Granger causality to this group but do not decompose the joint covariance structure of the five-variable system. This study fills that gap. PCA with full SVD is applied to a five-variable panel — CO₂, GDP, Fossil, Renew, Patents — for 2000–2022 (T=23, N=6). The σ₁/σ₂ ratio, the Differential Information Index (DII), ranges from 5.42 (Philippines) to 1.82 (Vietnam), identifying three structural groups. High-DII countries — Indonesia (5.22) and Philippines (5.42) — are effectively single-mode: one dominant axis absorbs over 95% of variance. Their independent axis V₂ carries a negative CO₂ loading, indicating a structurally available but weak decoupling pathway. Intermediate-DII countries — Malaysia (2.90) and Singapore (1.99) — show meaningful secondary structure. Malaysia's V₂ loads CO₂ at −0.867, the strongest decoupling signal in the ASEAN panel. Singapore's V₂ loads CO₂ at +0.950. Singapore is the only ASEAN country with a carbon-amplifying independent axis: LNG-dominated generation sustains CO₂ independently of income growth. Low-DII countries — Thailand (1.96) and Vietnam (1.82) — carry the richest differential information. Thailand's V₂ loads CO₂ at +0.666 and Fossil at +0.545: a fossil lock-in axis structurally separate from its renewable expansion. Vietnam's V₂ loads Renew at +0.669, confirming its post-2017 renewable surge constitutes a structurally independent axis. The pooled SVD (N=138) yields a principal axis of fossil-income development (85.6%) and an independent axis of innovation-renewable decoupling (11.9%). Singapore anchors the high end of pooled PC1 at +3.92; Vietnam anchors the low end at −1.78.