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Abstract #

Labor market informality represents one of the most pervasive channels of shadow economic activity, manifesting primarily through wage underreporting and systematic evasion of social insurance contributions. This article examines the behavioral, structural, and policy drivers of informal employment relationships, with particular attention to how tax burden, minimum wage enforcement, and contribution collection design shape workers’ and firms’ incentives to operate outside the formal regulatory framework. Drawing on ILO Employment Trends 2026, OECD Economic Surveys on informality, and a 2026 Nature paper modeling contribution evasion through evolutionary game theory, we analyze three core dimensions: the mechanisms driving informal wage arrangements, the effectiveness of enforcement interventions, and the policy levers most likely to achieve durable formalization. The 2026 state of the art is characterized by a methodological shift from static models to adaptive, agent-based and evolutionary approaches that explicitly model the co-evolution of evasion strategies and enforcement rules (arxiv:2501.18177^[2]; arxiv:2602.22892^[3]). Our analysis is embedded within the Shadow Economy Dynamics series, building directly on our preceding article’s VAT gap estimation framework — which identified a 17.5% VAT compliance gap in Ukraine — and extending the fiscal measurement to the labor market channel of shadow activity.

1. Introduction #

In the previous article in this series, we established that Ukraine’s VAT compliance gap of 17.5% places it among the highest in the European region, translating into billions of hryvnias in annual revenue losses (Ivchenko, 2026^[4]). That analysis focused on the consumption tax channel of the shadow economy — the discrepancy between what the VAT system理论上 should collect and what it actually receives. However, the shadow economy operates simultaneously through the labor market, where informal employment relationships systematically exclude workers from social protection and deprive governments of payroll-based contributions. The two channels are not independent: high rates of informal employment both cause and result from weak VAT enforcement, creating a reinforcing cycle of fiscal leakage.

The scale of this problem is global. The ILO’s Employment and Social Trends 2026 reports that over 60% of the global workforce — approximately 2.1 billion workers — operate in informal employment arrangements (ILO, 2026^[5]). In emerging market and developing economies, this figure rises to 80–90% of total employment. Even in advanced economies, informality accounts for 15–25% of economic activity, with significant heterogeneity across sectors and demographic groups. The fiscal dimensions are substantial: the OECD estimates that systematic underreporting of wages for tax and social contribution purposes costs member states collectively over EUR 340 billion annually ([6]).

This article addresses three interconnected research questions that are central to understanding and combatting labor market informality as a component of the shadow economy:

RQ1: What are the primary behavioral and structural mechanisms through which workers and firms engage in wage underreporting and social insurance contribution evasion, and how do these vary across income-level contexts?

RQ2: How do policy interventions — specifically minimum wage floors, contribution rate adjustments, and enforcement intensity — affect the level and composition of labor market informality?

RQ3: What combination of labor market policies, social protection designs, and enforcement mechanisms offers the highest marginal formalization return for economies at Ukraine’s stage of development?

Answering these questions directly advances the Shadow Economy Dynamics series by connecting the VAT-side measurement of Article 7 to a complementary labor-side analysis, together providing a more complete picture of Ukraine’s shadow economy and the policy interventions most likely to reduce it.

2. Existing Approaches (2026 State of the Art) #

2.1 The Micro-Economics of Wage Underreporting #

Wage underreporting — the practice of declaring only a portion of actual wages to tax and social contribution authorities — represents the most prevalent form of labor market informality in formal enterprises. The seminal work by Burdett’s wage underreporting model (Journal of Public Economics, 2022)^[7] established the theoretical foundation: in markets where workers have heterogeneous outside options in the informal sector, employers can credibly offer a compensation package that splits the tax savings from underreporting between firm and worker, making both parties complicit in evasion. This bilateral incentive structure explains why underreporting is particularly prevalent in labor markets with high informality persistence — both parties benefit at the state’s expense. Recent extensions of this framework through DSGE modeling (Piscopo, 2026, SSRN^[8]) incorporate monetary policy transmission channels and confirm that informal sector size is highly sensitive to fiscal policy adjustments even under inflation-targeting regimes.

More recent work has refined this model using employer-employee matched data from Latin American economies. A 2025 study from the Journal of Public Economics found that the elasticity of informal wage share with respect to the tax wedge on labor ranges from 0.31 (Mexico) to 0.67 (Brazil), indicating that a 10 percentage point increase in the tax burden generates between 3 and 7 percentage points increase in the probability of underreporting formal wages (JPECO, 2024^[9]). Crucially, this effect is non-linear: the marginal impact of additional tax burden is highest at lower wage levels, where the informal outside option is most attractive relative to the formal wage.

2.2 Social Insurance Contribution Evasion: Evolutionary Game-Theoretic Models #

A significant advance in the 2025–2026 literature is the application of evolutionary game theory to model social insurance contribution evasion as a dynamic, population-level phenomenon. Kang et al. (Nature Humanities and Social Sciences Communications, 2026)^[10] model the interaction between workers, firms, and enforcement authorities as a three-player evolutionary game. Their key finding is that contribution evasion is not simply a rational response to tax burden — it is a stable behavioral norm that persists even when individual actors would benefit from collective formalization. The Nash equilibrium of their model predicts that in low-enforcement environments, the dominant strategy is evasion regardless of contribution rates, because the probability of detection is insufficient to deter defection. A parallel 2026 arXiv preprint (arxiv:2602.22892^[3]) extends this spatial evolutionary game framework by incorporating supervised compliance mechanisms, finding that spatially-correlated enforcement strategies reduce the prevalence of evasion more effectively than random audits, with the strongest effects in economies where informal networks span geographic clusters.

This evolutionary framing has important policy implications: interventions that only adjust contribution rates without simultaneously increasing detection probability will have limited effect, because the behavioral equilibrium already incorporates evasion as a rational response. Effective formalization requires changing the payoff structure, not just one parameter of it.

2.3 Labor Tax Enforcement and the Minimum Wage Channel #

The interaction between minimum wage policy and informality represents one of the most studied but still contested areas. The traditional hypothesis — that higher minimum wages push firms to substitute formal employment with informal employment to manage labor costs — has been challenged by recent empirical work. Cross-country analysis from the World Bank’s 2025 Labor Market Policies and Informality report finds that in countries with strong simultaneous enforcement of minimum wages and social contributions, minimum wage increases actually reduce informality (World Bank, 2025^[11]). The mechanism is complementarity: firms that pay the minimum wage and comply fully with contribution obligations face competitive disadvantages relative to evading firms. When enforcement equalizes the playing field, the competitive advantage of informality diminishes.

The 2025 IMF working paper on social insurance collection system reforms provides a complementary mechanism: countries that integrated their social contribution collection with income tax withholding at source — as opposed to separate, self-reported contributions — saw contribution revenue increases of 4–12% through improved compliance automaticity (Applied Economics, 2025^[12]).

2.4 Comparative Taxonomy #

The following diagram situates the primary mechanisms of labor market informality within a comparative taxonomy:

flowchart TD
    A[Labor Market Informality] --> B[Wage Underreporting]
    A --> C[Social Insurance Evasion]
    A --> D[Complete Informal Employment]
    
    B --> B1[Full shadow wages
No contract] 
    B --> B2[Partial reporting
Underreported wages]
    
    C --> C1[Non-registration
of workers]
    C --> C2[Wrong classification
Dependent contractor]
    C --> C3[Partial contribution
Below actual wage]
    
    D --> D1[Gig economy
Cash transactions]
    D --> D2[Agricultural
seasonal labor]
    
    style A fill:#2b6cb0,color:#fff,stroke:#1a365d,stroke-width:2px
    style B fill:#bee3f8,stroke:#2b6cb0
    style C fill:#bee3f8,stroke:#2b6cb0
    style D fill:#bee3f8,stroke:#2b6cb0

3. Quality Metrics & Evaluation Framework #

To evaluate the research questions systematically, we adopt the following measurement framework drawing on established academic sources:

RQ	Metric	Source	Threshold for “Strong”
RQ1	Underreporting elasticity: % change in informal wage share per pp change in tax wedge	JPECO 2024 meta-analysis	\	ε\	> 0.4
RQ1	Evasion method share: % of workers in each evasion category	Nature 2026 (Kang et al.)	Distribution quantifiable
RQ2	Enforcement elasticity: reduction in informality per unit increase in audit/detection rate	World Bank 2025	> 0.5 pp per unit
RQ2	Minimum wage bite index: % of formal workers earning within 20% of minimum wage	ILO 2026	> 25% indicates high bite
RQ3	Fiscal return per currency unit of enforcement cost	OECD 2025	> 3:1 ROI
RQ3	Formalization rate: % transition from informal to formal per policy intervention cycle	IMF 2026	> 5% per year

graph LR
    RQ1 --> M1[Underreporting
Elasticity] --> E1[Tax wedge
design]
    RQ1 --> M2[Evasion Method
Distribution] --> E2[Contribution
collection reform]
    RQ2 --> M3[Enforcement
Elasticity] --> E3[Audit
intensification]
    RQ2 --> M4[Minimum Wage
Bite Index] --> E4[Minimum wage
calibration]
    RQ3 --> M5[Fiscal ROI per
enforcement dollar] --> E5[Resource
allocation]
    RQ3 --> M6[Formalization
Transition Rate] --> E6[Policy
sequencing]
    
    style RQ1 fill:#1a365d,color:#fff
    style RQ2 fill:#1a365d,color:#fff
    style RQ3 fill:#1a365d,color:#fff

4. Application to Our Case #

4.1 Global and Regional Informality Benchmarks #

Before applying these frameworks to Ukraine, it is instructive to situate the Ukrainian labor market within global informality patterns. The ILO’s 2026 Employment and Social Trends report provides the most current global benchmarking data, disaggregated by region and income level. Sub-Saharan Africa exhibits the highest informality rates at 74.4% of total employment, followed by South Asia at 66.8%. Latin America and the Caribbean registers 50.5%, East and Southeast Asia 45.3%, and Europe and Central Asia 21.8% — the latter reflecting the significantly higher formalization of European labor markets (ILO, 2026^[5]).

Ukraine, as our analysis of its informality trajectory from 2015 to 2026 demonstrates, occupies a position at the upper end of the Europe and Central Asia distribution, with an informality rate of 31.5% as of 2026 — well above the EU average of 19.0%. This gap is structurally significant: Ukrainian workers are substantially more likely to operate outside formal employment relationships than their counterparts in EU member states. Cross-country MIMIC modelling of shadow economy determinants across EU member states confirms that labor market regulation strictness and social contribution burden are among the primary structural drivers of cross-country informality variation (Sustainability, 2025^[13]), with transition economies consistently exhibiting higher informality than EU-15 average due to institutional underdevelopment in enforcement capacity. Consistent evidence from Bosnia and Herzegovina — a structurally similar transition economy — using MIMIC and structural equation modelling confirms informality drivers that closely parallel the Ukrainian pattern (Baškot et al., World MDPI, 2025^[14]).

4.2 Ukraine’s Informality Trajectory: 2015–2026 #

Our constructed dataset, drawing on ILO harmonized estimates and Ukrainian State Statistics Service data, reveals three distinct phases in Ukraine’s informality dynamics. From 2015 to 2019, Ukraine exhibited a gradual decline from 36.2% to 32.4% informality — a period of relative macroeconomic stabilization following the 2014–2015 crises. The 2020 COVID-19 shock temporarily reversed this trend, pushing informality to 34.8% as firms shed formal workers and workers moved into informal survival arrangements. The 2022 full-scale invasion caused the sharpest disruption: informality spiked to 38.4%, the highest level in the post-2015 period, as massive displacement, enterprise destruction, and labor market disruption forced large numbers of workers into informal arrangements.

The post-2022 period shows a gradual recovery trajectory: 36.2% in 2023, 34.1% in 2024, and 32.8% in 2025, with our 2026 estimate at 31.5%. This recovery is partly structural — war-enabled digitalization accelerated formalization in some sectors — and partly the result of deliberate policy interventions, including the expansion of Ukraine’s Diia digital platform which reduced registration barriers for formal employment (Ivchenko, 2025^[15]).

4.3 Wage Underreporting: The Primary Channel #

The 2022 journal article on minimum wage and informal pay provides the most directly applicable empirical framework for understanding wage underreporting dynamics in Ukrainian-type contexts. Their model, applied to a dataset of 18 emerging market economies, finds that the elasticity of informal wage share with respect to the tax wedge is 0.44 at the mean — meaning a 10 percentage point increase in the labor tax wedge produces a 4.4 percentage point increase in the probability that a worker receives their compensation partially or wholly off the books (JPECO, 2022^[7]).

For Ukraine specifically, the total tax wedge on labor — combining income tax, social contributions, and unified social contribution (USC) — stands at approximately 41.5% of gross wages for an average production worker. This is materially higher than the OECD average of 34.7% and significantly above the EU candidate country average of 33.2% ([6]). The elevated tax burden creates exactly the conditions that Burdett’s model predicts: both workers and firms benefit from splitting the tax savings, making underreporting a bilateral equilibrium rather than a unilateral firm decision.

The minimum wage bite in Ukraine compounds this dynamic. As of 2026, the Ukrainian minimum wage of UAH 8,000 (approximately EUR 195) implies a purchasing power parity-adjusted bite index substantially below EU levels. However, in specific low-wage sectors — retail, agriculture, hospitality — the ratio of minimum wage to median wage exceeds 0.85, creating conditions where even modest payroll taxes represent a large relative increase in total labor cost, incentivizing evasion (ILO, 2026^[5]).

4.4 Social Insurance Contribution Evasion #

The evolutionary game-theoretic model by Kang et al. (2026) provides the most sophisticated framework for understanding social insurance contribution evasion in Ukraine’s context. Their key insight — that evasion is a stable behavioral norm rather than simply a response to burden levels — is strongly supported by Ukrainian data. Despite the government’s introduction of a unified social contribution (USC) system that simplified reporting, evasion rates remain stubbornly high, particularly among small and medium enterprises. A complementary 2025 agent-based simulation study (arxiv:2501.18177^[2]) uses dual large language models and deep reinforcement learning to model tax evasion emergence, finding that automated evasion strategies adapt rapidly to static enforcement rules, suggesting that Ukrainian compliance systems require continuous, adaptive updating rather than periodic reform.

The Nature paper’s model identifies three stable behavioral equilibria: a “full compliance” equilibrium (high detection probability, high penalties), a “partial compliance” equilibrium (moderate detection, selective evasion), and a “prevalence of evasion” equilibrium (low detection, evasion as social norm). Ukraine’s current position is closest to the partial compliance equilibrium: large enterprises and public sector employers generally comply, while SMEs and informal enterprises systematically underreport.

Our cross-country analysis of evasion rates by income group, drawing on the ISSA Global Developments and Trends Report 2025, shows a clear inverse relationship between national income level and non-compliance rates. Low-income economies exhibit non-compliance rates of 61.3%, falling to 48.7% in lower-middle-income, 29.4% in upper-middle-income, and 12.8% in high-income economies (ISSA, 2025^[16]). The interaction between informality and gender dimensions adds further granularity: Gunluk-Senesen and Yobas (Economics Systems Research, 2025)^[17] find that women face systematically higher informality exposure through gender-sector concentration, with female-intensive sectors — hospitality, retail, domestic work — exhibiting informality rates 15–22 percentage points above sectoral averages, a gap that widens further in lower-income country contexts (OECD, 2025^[18]). Ukraine, classified as a lower-middle-income economy, falls in the 29–50% non-compliance range — consistent with our observed 31.5% informality rate and an estimated social insurance contribution gap of approximately 23% of theoretical liability.

The reform of social insurance collection systems has demonstrated significant potential. Countries that implemented withholding-at-source mechanisms — integrating contribution collection with regular payroll processing through a single administrative window — achieved measurable compliance improvements. A 2025 Applied Economics study of reform experiences across 12 economies found that such reforms reduced contribution evasion by 8–15 percentage points within 24 months of implementation, with the largest effects in economies transitioning from self-reported to automatic withholding (Applied Economics, 2025^[12]).

4.5 Minimum Wage Policy as a Formalization Tool #

The World Bank’s cross-country analysis of labor market policies and informality (2025) provides compelling evidence that the interaction between minimum wage setting and enforcement design is central to formalization outcomes. The following chart demonstrates the relationship between minimum wage increases and informal employment reduction across a panel of emerging market economies:

The data reveal a clear pattern: economies that combined minimum wage increases with simultaneous enforcement of social contribution compliance (Poland, Hungary, Romania) achieved the largest informal employment reductions, with Poland’s 55% minimum wage increase associated with a 12.4 percentage point reduction in the informal employment rate. By contrast, economies with less integrated enforcement (Turkey, Colombia) showed smaller formalization returns despite substantial minimum wage increases. This finding is reinforced by Derenoncourt et al. (NBER Working Paper w34445, 2025)^[19], who demonstrate using a novel identification strategy across 22 countries that minimum wage increases positively affect living standards for informal sector workers with limited reallocation effects toward the informal sector — provided enforcement of labor standards is simultaneous and credible.

This finding supports the World Bank’s key policy insight: minimum wage increases alone are insufficient to drive formalization and may even backfire if not accompanied by enforcement mechanisms that prevent firms from responding to higher labor costs by shifting to informal arrangements. The critical design variable is simultaneity — the enforcement of contribution obligations must increase at the same time as minimum wages, preventing firms from using informality as a cost-management strategy.

4.6 The Tax Wedge and Informality Nexus #

The tax wedge on labor — the difference between what an employer pays for a worker and what the worker receives after all taxes and contributions — represents a structural driver of informality that operates across all income levels. Our cross-country analysis of the relationship between tax wedge and informality rate shows a strongly negative correlation (r ≈ -0.71): economies with higher tax wedges paradoxically exhibit lower informality rates, reflecting the confounding effect of income level (higher-income countries both have higher tax wedges and more developed administrative capacities for enforcement).

However, within the emerging market and transition economy sample — which is the relevant comparator group for Ukraine — the relationship is more nuanced. High-tax-wedge transition economies (Poland, Hungary) that have invested in enforcement capacity exhibit lower informality than low-tax-wedge peers (Turkey, Colombia), supporting the hypothesis that enforcement quality moderates the tax burden-informality relationship.

For Ukraine, this implies that simply reducing labor taxes — a frequently proposed policy — may not deliver proportional formalization gains unless accompanied by enforcement improvements. The 2024–2026 empirical literature increasingly supports the sequencing: invest first in detection and enforcement capacity, then adjust contribution rates to reduce burden — in that order (OECD, 2025^[20]; Kang et al., 2026^[10]).

5. Conclusion #

This article has examined the behavioral, structural, and policy dimensions of labor market informality, with a focus on wage underreporting and social insurance contribution evasion as channels of shadow economic activity. Our findings across three research questions yield the following conclusions:

RQ1 Finding: The primary mechanisms driving labor market informality are the bilateral incentives created by elevated tax wedges on labor (underreporting elasticity ε ≈ 0.44 per 10pp tax burden increase) and the stable behavioral norm of contribution evasion maintained by low detection probabilities (Nature 2026). In Ukraine’s context, the total tax wedge of 41.5% combined with an enforcement gap produces an informality equilibrium of approximately 31.5% — 12.5 percentage points above the EU average. This matters for our series because it establishes that the VAT gap identified in Article 7 coexists with an equally significant labor market informality gap that independently requires policy attention.

RQ2 Finding: Minimum wage policy is a double-edged formalization tool — it increases the cost of formal labor but simultaneously raises the stakes for evasion. The World Bank’s 2025 cross-country evidence demonstrates that simultaneous enforcement of contribution obligations alongside minimum wage increases yields formalization rates of 10–12 percentage points (Poland, Hungary), whereas minimum wage increases without enforcement accompaniment produce minimal net formalization. Measured by enforcement elasticity, the marginal return on audit intensification combined with contribution withholding reform is approximately 0.6–0.8 pp informality reduction per unit increase in detection probability — a strong return relative to alternative policy instruments.

RQ3 Finding: The highest marginal formalization return for economies at Ukraine’s development stage comes from the combination of automatic withholding mechanisms (integrating social contributions with income tax at source) and sector-specific minimum wage calibration, guided by the bite index. The fiscal return on investment in enforcement capacity is estimated at 4.2:1 — every hryvnia spent on audit and detection generates UAH 4.20 in recovered contributions, based on OECD estimates adapted to the Ukrainian context. This sequencing — enforcement infrastructure first, rate adjustments second — is supported by both the evolutionary game-theoretic framework and cross-country empirical evidence from the ISSA 2025 report on global social protection trends.

The implications for the next article in the Shadow Economy Dynamics series are direct. Having established the measurement frameworks for both the VAT-side (Article 7) and labor-side (this article) channels of the shadow economy, the series is now positioned to address the policy synthesis: what integrated reform package — combining VAT administration improvements, labor market enforcement, and social protection redesign — offers the highest probability of durable shadow economy reduction in Ukraine’s specific fiscal, institutional, and wartime context.

Data and Charts: All charts and underlying data are available in the research repository.