Ranking of the six research gaps

Scores use a five-point scale, where 5 is most favorable. Novelty measures how explicitly the literature leaves the question unresolved; policy relevance measures proximity to fiscal or environmental-policy decisions; data feasibility measures the plausibility of obtaining linked administrative, survey, or program data; causal-identification strength measures the availability of credible quasi-experimental or experimental designs; and JEL fit measures the clarity of a primary JEL classification. These are comparative research-design judgments, not estimates reported by the cited studies.

The JEL placements are direct matches to the AEA guide: H26 covers tax evasion and avoidance; H23 environmental taxes, subsidies, externalities, and redistributive effects; H54 public investment and infrastructure; O33 technology choices, consequences, and diffusion; Q58 environmental government policy; and C23 panel and spatio-temporal models. Environmental tax studies should be cross-classified under H23 and Q58. (JEL Classification Codes Guide, 2026)

Ranking rationale

1. Revenue realization and the VAT-credit mechanism — strongest thesis option

This topic combines unusually high policy relevance with unusually clean measurement. The Peruvian e-invoicing evaluation documents increased reported sales, purchases, and VAT liabilities, but shows that VAT-credit stocks offset the reform’s positive effect on collection. (Bellon, 2022) The same research says that available data cannot fully separate compliance from productivity changes. (Bellon, 2022) A thesis can make a narrow and publishable contribution by reconstructing the accounting chain from e-invoice issuance to assessed liability, credit accumulation, offsets, payment, arrears, refunds, and net revenue.

It ranks first because the dependent variables are administratively defined and the intervention can be anchored to staggered adoption dates. The core causal design can be an event study or difference-in-differences model, strengthened by tests for differential pre-trends and by separating gross liabilities from cash collections. The central result would be directly useful to a revenue authority deciding whether digitalization must be paired with credit-management, refund, or audit reform. Its main constraint is data access, but it does not require transaction-network identifiers, which makes it more achievable than the spillover topic.

2. Tax-network spillovers from electronic invoicing — strongest novelty–identification combination

This is the most novel topic because the original Peru study explicitly identifies upstream and downstream spillovers of e-invoicing as a future research avenue. It also notes that the source data excludes micro firms below the eligibility threshold and informal firms outside tax registration. (Bellon, 2022) The gap is consequential: direct adopters may change the compliance incentives of suppliers and customers, so firm-level estimates can understate or misallocate the aggregate tax-base effect.

The identification opportunity is strong if invoice-level or buyer–supplier records can be linked to staggered mandates. Exposure to treated trading partners provides a pre-specified network treatment, while adoption thresholds and phased rollout support event-time analysis. This topic ranks second, rather than first, because access to linked transactions and credible handling of endogenous network formation are demanding. For a doctoral thesis with a tax authority partnership, it could be the best choice; for a shorter master’s thesis, the first-ranked topic is safer.

3. Distributional incidence and acceptance of environmental taxes — strongest interdisciplinary policy paper

The environmental-policy literature identifies unresolved distributional contradictions: a systematic review finds mixed evidence for energy-tax incidence and high disagreement for emissions-allowance schemes. It concludes that policy-design differences explain many contradictory results beyond differences in methods, sectors, or settings. (Peñasco, 2021) Separately, an environmental-tax acceptance review finds that support is associated with understanding policy and revenue use, government trust, perceived fairness, and climate concern. (Muhammad, 2021) It specifically calls for research on trust predictors, tax morale, economic perceptions, and fiscal-psychology mechanisms. (Muhammad, 2021)

The publishable contribution is to join incidence and political acceptability in one design. Link household expenditure microdata to a survey or randomized information experiment that varies the salience and form of revenue recycling. Estimate burdens by income, location, and energy use alongside support, trust, and behavioral response. This ranks third because household linkage and a reform setting are more difficult than tax-administration data, but it makes a direct public-finance and environmental-policy contribution. The AEA guide assigns environmental externalities from taxes and subsidies to H23 and Q58. (JEL Classification Codes Guide, 2026)

4. Green public expenditure in under-studied regions — high impact, lower near-term feasibility

This topic has the highest policy ambition. The decarbonization-policy review identifies sparse evidence outside OECD countries, particularly in Sub-Saharan Africa and the Middle East, and very few distributional evaluations of procurement, auctions, and public R&D. (Peñasco, 2021) A study of the distributional effects of green procurement or auctions would directly address this documented evidence deficit.

It ranks fourth because credible cross-country comparisons face heterogeneous institutions, procurement systems, and outcome measurement. A strong paper is feasible if narrowed to one country and one program with an eligibility threshold, geographic rollout, or auction rule that creates quasi-experimental variation. It is better suited to a thesis with field access or a government partner than to a project relying solely on public aggregate data.

5. Environmental and firm-performance effects of digital transformation — novel but measurement-intensive

A systematic review concludes that environmental effects of digital transformation remain uncertain and that the literature has not answered how digitalization of environmental sustainability affects overall firm performance. (Feroz, 2021) This gap is important because the same label can cover heterogeneous technologies and channels: monitoring, waste management, production optimization, or resource-intensive expansion.

The limitation is construct validity. A publishable design needs technology-specific adoption measures plus energy, materials, waste, emissions, productivity, and profitability at the establishment level. Without those, the study risks equating technology adoption with environmental improvement. It should be selected when proprietary firm data and a clear adoption shock are available; otherwise it is lower-priority than the first three topics.

6. Strategic governance of sustainable digitalization — theoretically valuable but causally weakest

The review reports insufficient attention to the capabilities needed for environmentally sustainable digital transformation and no account of how environmental sustainability enters strategic decision-making. (Feroz, 2021) This is a valid and original gap, but board-level strategy, capability, and decision rights are difficult to measure consistently and are strongly endogenous to firm performance.

The best route is a mixed-method thesis: validated executive survey measures, qualitative process tracing, and a panel analysis around disclosure mandates or digital-investment incentives. It ranks sixth because it is likely to yield rich governance evidence but weaker causal claims than the policy-rollout and administrative-data topics above.

Recommendation: top three

Choose Topic 1 for a thesis with a realistic path to a publishable applied-public-finance paper. It asks a sharply defined fiscal question, relies on administratively meaningful outcomes, and supports a transparent quasi-experimental design.

Choose Topic 2 when linked transaction data and an institutional partnership are available. Its explicit future-research status, strong identification potential, and relevance to compliance diffusion give it the largest originality payoff, but also the highest implementation risk among the top three.

Choose Topic 3 for an interdisciplinary public-finance/environmental-economics thesis. It directly addresses documented disagreement in incidence evidence and connects tax design to legitimacy, fairness, and revenue recycling. Its strongest version is a household panel plus randomized policy-information or rebate framing, rather than a stand-alone opinion survey.

Generated Outputs

ranking-evidence.json — file unavailable

Sensitivity analysis of the six research gaps

The reassessment retains the prior 1–5 criterion scores and changes only the weights. Data feasibility receives the largest weight in every decision scenario because it determines whether a thesis can be completed with accessible, linkable, and sufficiently granular data. The e-invoicing study uses administrative VAT data but excludes micro and informal firms, cannot fully separate compliance from productivity, and identifies upstream and downstream spillovers as a future research question. (Bellon, 2022) The green-policy review identifies sparse regional coverage and limited distributional evaluations for some instruments. (Peñasco, 2021) The digital-transformation review reports uncertain environmental effects and unanswered firm-performance questions. (Feroz, 2021)

Fixed criterion scores

These are comparative design assessments, not effect-size estimates. A score of 5 means more favorable for the criterion. The JEL-fit score assesses whether the central contribution maps cleanly onto a defined JEL field or subfield, not whether only one code is permissible.

The JEL guide defines H26 for tax evasion and avoidance, O33 for technological change and diffusion, H23 for environmental taxes and subsidies, Q58 for environmental government policy, H54 for public investment and infrastructure, and C23 for panel and spatio-temporal models. (JEL Classification Codes Guide, 2026)

Weight scenarios and rankings

Each weighted score is the sum of criterion score × weight; scores are rescaled to a 1–5 range. DF denotes data feasibility and CID causal-identification strength. The final column records whether the original top-three set—Topics 1, 2, and 3—changes.

What the sensitivity analysis shows

The core recommendation is robust when feasibility is dominant. In the two scenarios that most heavily prioritize data feasibility, Topics 1, 2, and 3 remain the leading set. The e-invoicing evaluation reports increased firm sales, purchases, and VAT liabilities, while existing VAT-credit stocks offset positive effects on VAT collection. (Bellon, 2022) The first-place ranking is a design judgment: it favors a project when tax microdata and an institutional partner are available to measure liabilities, credits, offsets, and collections.

Topic 2 is second in all feasibility and identification scenarios, but it is conditional on data access.

The underlying study explicitly identifies upstream and downstream e-invoicing spillovers as a future research avenue. (Bellon, 2022)

Its score of 4 for data feasibility is a design judgment: a spillover study requires observation of supplier–customer links and credible treatment of endogenous trading relationships. If transaction-level links are unavailable, Topic 2 should be demoted below Topic 3.

Topic 3 is the most stable environmental-economics choice.

The policy review reports mixed evidence on distributional effects of energy taxes and high disagreement among the reviewed evaluations of emissions-allowance schemes. (Peñasco, 2021) The acceptance review identifies policy information and revenue use, trust, perceived fairness, and climate concern as factors associated with support. (Muhammad, 2021) It calls for research on trust predictors, tax morale, economic perceptions, and fiscal-psychology mechanisms. (Muhammad, 2021)

These explicit gaps support a project that combines household incidence with revenue-recycling and acceptance measures. Its feasibility score of 3 is a design judgment reflecting the need to integrate expenditure data with survey or experimental data.

Topic 4 challenges the top three under a novelty-and-policy objective.

The review documents sparse coverage outside OECD settings and limited distributional evidence for government procurement, auctions, and R&D. (Peñasco, 2021)

Its score of 5 for novelty and policy relevance is a comparative judgment based on that documented evidence gap. It falls under feasibility-heavy weights because the proposed cross-jurisdiction program and outcome data are demanding. A single-country procurement or auction study with an eligibility rule, geographic rollout, or other discontinuity would materially strengthen the design.

Topics 5 and 6 are valuable but are not preferred for a data-feasible thesis.

The digital-transformation review reports uncertain environmental effects and unanswered firm-performance questions. (Feroz, 2021) It also reports insufficient attention to relevant capabilities and no account of how sustainability practices become part of strategic decision-making. (Feroz, 2021)

The lower rankings are design judgments: the projects require technology-specific adoption measures, environmental outcomes, and hard-to-observe organizational constructs. Topic 5 is preferable to Topic 6 when establishment-level adoption and environmental-accounting data are available; Topic 6 is better suited to a mixed-method governance dissertation than a short causal paper.

Decision rule and revised recommendation

1. Select Topic 1, revenue realization and the VAT-credit mechanism, as the first choice when administrative tax data are obtainable. It has the highest score in every scenario and the clearest route from an observed digital reform to a fiscal outcome.
2. Select Topic 2, e-invoicing network spillovers, only with invoice-level buyer–supplier data. Under that condition it is the strongest novelty–identification contribution. Without those links, replace it with Topic 3.
3. Select Topic 3, environmental-tax incidence and acceptance, as the default interdisciplinary choice. It remains in the top three under the feasibility-dominant scenario. The AEA guide cross-classifies environmental externalities from taxes and subsidies under H23 and Q58. (JEL Classification Codes Guide, 2026)
4. Elevate Topic 4 only when the thesis objective favors novelty and policy influence over near-term data certainty, and when a defined program offers a credible quasi-experimental design.

Thus, data feasibility does not overturn the earlier recommendation; it strengthens it. The ranking should be treated as conditional: Topic 1 is robustly first, Topic 3 is the safest environmental-economics option, and Topic 2 is the highest-upside but data-contingent choice.

Practical decision matrix and citation audit

Decision matrix for Topics 1–4

The ratings below are project-design judgments on a 1–5 scale, where 5 means more feasible or lower risk. Evidence statements are distinguished from these judgments. The e-invoicing evidence is based on administrative VAT data for formal firms but excludes micro firms below the eligibility threshold and unregistered informal firms; it also cannot fully separate compliance from productivity changes. (Bellon, 2022) The environmental-policy review documents sparse geographic coverage outside OECD countries and limited distributional evaluations for procurement, auctions, and public R&D. (Peñasco, 2021)

Evidence basis for the matrix

Topic 1 is supported by the direct e-invoicing result: the Peru evaluation reports increased reported sales, purchases, and VAT liabilities in the first year, while existing VAT-credit stocks offset the reform’s positive effect on VAT collection. (Bellon, 2022) That distinction makes a linked liability–credit–payment panel the decisive dataset, rather than invoice adoption alone. The study itself names upstream and downstream e-invoicing spillovers as a future research avenue, which provides the literature basis for Topic 2. (Bellon, 2022)

Topic 3 responds to two documented evidence problems. The decarbonization-policy review finds mixed distributional evidence for energy taxes and high disagreement among evaluations of emissions-allowance schemes. (Peñasco, 2021) The environmental-tax acceptance review finds that support is higher when people are informed about policy effectiveness and content, particularly revenue use; trust government; perceive costs and social sharing as fair; and are concerned about climate change. (Muhammad, 2021) The review calls for research on predictors of trust, tax morale, economic perceptions, fiscal psychology, and theory-of-planned-behavior variables. (Muhammad, 2021) Topic 4 is justified by the review’s limited distributional evidence for procurement, auctions, and public R&D, and its sparse coverage outside OECD countries. (Peñasco, 2021)

Recommendation conditional on available data

Citation audit of the reassessment

The audit leaves the empirical foundation intact but narrows the strongest claims. The literature supports the e-invoicing mechanisms and exclusions, the environmental-tax evidence conflict and acceptance mechanisms, the digitalization uncertainties, and the JEL classifications. Dataset access, score values, and rank changes are transparent decision assumptions that should be revised once a specific country, agency partner, and data-access pathway are known.