1. The Changing Sociology of the Profession

The production function of economic knowledge was, for a long time, labor-intensive but capital-light, requiring little more than a library, a pen, and a singular, powerful intellect. However, as noted by Lovell (1973), the cumulative stock of journal articles in economics has historically doubled every fourteen years. This explosion has not merely increased output volume—it has fundamentally altered the mechanism of production.

The solitary scholar is being replaced by the research team. The qualitative treatise is being supplanted by the quantitative model. The reliance on introspection is giving way to dependence on external funding. To understand these drivers, we must look beyond aggregate statistics and examine the micro-foundations of collaboration within specific, high-growth domains.

2. Why Environmental Economics?

Previous bibliometric studies have consistently identified Environmental and Resource Economics (ERE) as a distinct outlier in collaboration patterns. The propensity for teamwork is likely endogenous to the subject matter. Environmental problems are inherently complex, coupled systems involving human behavior, natural laws, and institutional constraints.

The study of climate change, for instance, requires understanding not just discount rates and utility functions, but also carbon cycles, atmospheric decay, and technological innovation curves. As Bjurström and Polk (2011) argue, the problem scope of climate change is broader than any single discipline, forcing the scientific community to draw on extensive knowledge from various fields. This "interdisciplinarity" acts as a centripetal force, pulling researchers together into teams.

3. The Evolution of JEEM (1974–2010)

Our dataset covers every article published in the Journal of Environmental Economics and Management (JEEM) from Volume 1 (1974) to Volume 60 (2010). This comprehensive census allows us to trace long-term secular trends in authorship, content, and demographics.

The "Inverted U" Anomaly

One of the most striking findings is the non-linear trajectory of single authorship in JEEM. In "core" general interest journals, the fraction of single-authored papers declined monotonically from ~75% (1974) to ~25% (2010). JEEM tells a different story.

In its inaugural volumes, single-authored papers were remarkably low—approximately 38%—indicating that environmental economics was born as a collaborative enterprise. However, following this initial burst, JEEM bucked the trend. Single authorship increased until reaching a historic peak of approximately 72% in 1988.

Post-1988, the gravity of the broader profession took hold. Single-authored papers began a precipitous decline, dropping from that 72% high to only 15% by 2008. This sharp V-shape signifies a regime change: the transition from a theoretical founding era to an empirical, "big science" era.

The Rise of the Team

Parallel to the decline in single authors is the expansion of team size. In 1974, the average JEEM article was written by 1.71 authors—significantly higher than the 1.28 average in core journals. By 2009, this rose to approximately 2.5 authors. A standard mean-comparison test confirmed the mean number of authors was statistically significantly higher for JEEM than for general economics journals (t-value = -9.96).

The Empirical Turn

What drove this shift? We categorized every article into four types:

• Qualitative: Surveys, case studies without econometrics
• Theoretical: Pure modeling, simulation with artificial data
• Quantitative: Purely empirical work using real data
• Theoretical + Empirical: The modern "gold standard"

By 2000, qualitative papers had effectively vanished. The share of purely theoretical articles declined. Empirical work surged. The implications for collaboration are profound—empirical work involves distinct high-fixed-cost activities: data collection, cleaning, coding, and estimation. This necessitates a division of labor.

4. Five Hypotheses on Collaboration

We model the decision to co-author as a rational economic choice, testing five core hypotheses:

Hypothesis 1: Division of Labor

Dating back to Adam Smith, this posits that as the "market" for economic knowledge expands, specialization becomes necessary. A researcher may specialize in dynamic optimization (theory) while another specializes in non-parametric estimation (empirics). Neither can produce a complete paper alone that meets modern standards.

✓ Strongly Supported — Quantitative and Mixed papers are significantly more likely to be multi-authored. The count of Tables is a positive predictor; the count of Equations is not.

Hypothesis 2: Opportunity Cost of Time

As the pressure to publish increases, the cost of time rises. We test for a trade-off between formal co-authorship and informal assistance (acknowledgments).

✓ Supported — The variable ACKNOWLEDGE displays a significant negative coefficient. Authors substitute formal help (co-authors) for informal help (acknowledgments).

Hypothesis 3: The Quality Hypothesis

This views collaboration as a technology to maximize output quality—"two heads are better than one."

✗ Rejected — TOP10CITED is statistically insignificant. In JEEM, a single-authored paper is just as likely to be a "blockbuster" as a multi-authored one.

Hypothesis 4: Diversification Hypothesis

Adapted from portfolio theory: to minimize variance of output, researchers diversify by investing time across multiple co-authored papers rather than one single-authored work.

~ Inconclusive — Limited to 2000-2010 sample; positive sign observed but not robust.

Hypothesis 5: Competition for External Funding

A novel hypothesis: the material conditions of research—specifically the need for grant money—drive team formation. Grant agencies favor collaborative teams to ensure project viability.

✓ Strongly Supported — EXTERNALFUND is positive and significant at 1% across all models. Funding increases the probability of co-authorship by approximately 14%.

5. The Death of Distance

Perhaps the most dramatic shift is spatial. We analyzed whether co-authors were located at the same institution or were geographically distant (>100 miles apart):

• 1975: Only 16% of co-authored articles involved distant collaboration
• 2010: This share exploded to over 75%

This shift, facilitated by the internet and email, indicates a move from "convenience collaboration" to "specialized collaboration." Authors no longer partner with the nearest available economist—they partner with the best available specialist regardless of location. The market for co-authors has become global and liquid.

6. The Gender Effect

The entry of women into economics has been slow, but the trend in JEEM is positive. The fraction of articles with at least one female author rose from effectively 0% in the early 1970s to more than 30% by 2010.

Our Probit analysis reveals a distinct gender dimension: FEMALE has a significant positive marginal effect on co-authorship probability, increasing it by 13.4% to 16.1%. This aligns with literature suggesting women in economics may rely more on collaborative networks, potentially to navigate barriers in a male-dominated field.

7. Conclusion: The Future of the Discipline

This empirical investigation paints a portrait of a discipline that has undergone a profound industrial revolution. The romantic era of the environmental economist—the solitary philosopher reflecting on externalities—is effectively over. It has been replaced by a high-tech, capital-intensive, and highly collaborative enterprise driven by the imperatives of data, funding, and specialization.

Our analysis confirms that this transition is rational. Collaboration is an efficiency-enhancing response to the increasing "burden of knowledge." As environmental economics integrates more complex climate models, larger datasets, and more rigorous econometric identification strategies, the "Jack-of-all-trades" researcher has become obsolete.

As we look forward, the trend lines suggest that the average number of authors will continue to rise. As environmental economics merges further with "Big Data," machine learning, and natural sciences to tackle the climate crisis, the field will likely converge toward the "lab model" of the hard sciences, where papers with 5, 10, or 20 authors become the standard unit of scientific production.