What should be held steady in a steady-state economy? Interpreting Daly's definition at the national level

Within this article, I investigate a number of the conceptual issues that arise when attempting to translate Herman Daly's definition of a steady-state economy (SSE) into a set of national biophysical indicators. Although Daly's definition gives a high-level view of what would be held steady in an SSE, it also leaves many questions unanswered. How should stocks and flows be aggregated? What is the role of international trade? How should nonrenewable resources be treated? And where does natural capital fit in? To help answer these questions, I relate Daly's definition to key concepts and terminology from material and energy flow accounting. I explore topics such as aggregation, international trade, the relevance of throughput, and hidden flows. I conclude that a set of biophysical accounts for an SSE should include three types of indicators (stocks, flows, and scale), track how stocks and flows are changing over a 5- to 10-year period, use aggregated data that measure the quantity of resource use (rather than its quality), measure both total and nonrenewable resource use, adopt a consumption-based approach, include hidden flows, and exclude indicators that measure characteristics of the stock of natural capital (with the notable exception of indicators that measure the regenerative and assimilative capacities of ecosystems).