Between you and I: A portfolio theory of the circular economy
这篇概念性论文借用现代投资组合理论，解释了微观层面的资源循环利用如何加总为宏观层面的可持续资源使用，并识别了驱动因素和条件。
By using resources more circularly, individual resources users hope to contribute to a more eco-efficient and sustainable resource use. Whether resources are used sustainably is decided at the macro-level, raising the question if, as well as how, the efficient and circular use of resources at the micro-level adds up to their efficient and circular use on the macro-level. Currently, the link between the circular use of resources at micro- and macro-levels is under-theorized. The symbiotic relationship between individual resource users enables a reduction in the resource use at the macro-level. In this conceptual paper, we argue that an analogous link exists in finance where desirable investment return is linked to undesirable investment risk, and that via the generation of efficient portfolios, individual risks are at least partially diversified away. As our main contribution, we theorize the circular economy, both in its perfect and imperfect forms, using modern portfolio theory. Our theory identifies the drivers of circular resource use and shows under which conditions individual resource use contributes to the circular use of resources.