Three Reasons for Creating a Single Ocean Health Index

As the gross domestic product shows us, a single number that represents the health of a complex and dynamic system can have amazing and perhaps unexpected power.
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As the gross domestic product shows us, a single number that represents the health of a complex and dynamic system can have amazing and perhaps unexpected power.

Just over 75 years ago, there was no easy way to track how well a nation’s economy and its people were doing. Data from all kinds of measures existed, but it was hard to interpret what they all meant. Responding in part to the dramatic declines of the Great Depression, the U.S. Congress in 1934 asked renowned economist Simon Kuznets to develop a method for gauging the condition, or health, of the United States. He came up with what we now know as the gross domestic product, or GDP.

Although criticisms abound about its utility or appropriateness as a measure of national well-being (including from Kuznets himself), the use of GDP has had an indelible and transformative impact on global economics, policy, and markets.

But why is a single index necessary or useful? Instead, why not track how the individual components are doing? Perhaps the value has become evident in the case of GDP, but it’s worth diving deeper into that question since it’s the philosophical foundation for why we are creating an Ocean Health Index.

There are three reasons why it is essential to synthesize information into a single index:

1. It forces us to make explicit the relative importance of the different components that we are evaluating.

Why not just make them all equally important? No one actually does this. People inevitably value particular attributes over others, they just do it in their heads. Whether it's the national economy, choosing a vacation destination, or what to do on a Saturday afternoon, you assess the relative importance of all the variables you value before you make a final decision. When you take a date to a restaurant, you consider price, decor, type of food, noise level, how romantic the place is, and so on, and then decide based on which variable (or variables) is most important to you. In these cases, you are weighting the importance of different criteria and making a single decision.

Market researchers spend enormous amounts of money trying to understand what qualities are most important to people. In other words, they are trying to make explicit and quantitative the weights that people place on different decision criteria.

About the Project!

Ocean health means different things to different people, and current assessments of ocean health focus predominantly on the state of the natural environment. The Ocean Health Index project was founded by Conservation International, The National Geographic Society, New England Aquarium, and the National Center for Ecological Analysis and Synthesis. The project aims to develop a set of indicators that describe ocean health according to how people benefit from and affect marine ecosystems. Here are the articles has published on the subject:


The Making of the Ocean Health Index

Ocean Index Navigates Between the Politic, the Pristine

Setting Targets in the Ocean Health Index

Three Reasons for Creating a Single Ocean Health Index

Ocean Health Index Accounts for Human Benefits

Ocean Health Index: The Audacity of Necessity

Those of us creating the Ocean Health Index are doing exactly the same thing. By combining the very different goals people have for a healthy ocean into a single number, we force ourselves to make explicit how important each of those goals is to defining a healthy system; we crystallize the weights we place on the different components. Some people will care most about jobs and livelihoods, for example, while others will care more about biodiversity conservation and clean water. There is no right or wrong answer. We all have legitimately different views of what we want from a healthy ocean. However, we need to find ways to reconcile these conflicting views, as decisions about ocean use (and non-use) affect the well-being of all people, now and in the future.

This may seem a difficult challenge, but any environmental management decision faces this same issue. We plan to generate weightings for different goals in the OHI in at least three ways. Our hope is to understand how perceptions of ocean health might change when viewed through different lenses: assuming equal weights for different goals (probably not right for anyone, but at least it's egalitarian), creating weightings for the goals based on different hypothetical value sets (conservationist vs. resource extraction vs. sustainable user), and surveying people representing a diversity of interests related to the ocean along the U.S. West Coast.

2. It makes explicit and quantitative the trade-offs that occur among goals.

Although we divide and track each of the 10 public goals of ocean health separately, they are all connected by the biophysical world and human communities that underlie them. This vast network of connections and the limitations it necessarily imposes mean that the output of some goals go down when others go up. Every single decision related to ocean health — whether to limit or encourage coastal development, for example — has multiple consequences, some considered good and others bad depending on who is viewing them. Such trade-offs are ubiquitous in management and policymaking — if every situation were a win-win, politicians would be out of a job. By combining the goals into a single index, these trade-offs become quantitative and obvious, and far more informative for management decisions.

Take a situation where the provision of food from fisheries and aquaculture increases by 10 percent but this comes with a 10 percent decrease in biodiversity (a certain number of species or habitats are lost from the area). For those in need of a daily meal, this change will be seen as a welcome improvement; for those who cannot bear the loss of even a single species, that outcome would be disastrous. These issues, the bread and butter of economics and public policy, require boiling everything down to a single number to be able to fairly and quantitatively assess these trade-offs. Doing so gives perspective on how disparate changes influence the big picture.

3. It’s a much-needed communication device.

GDP has transformed the way we think about the health of a nation (and has inspired numerous alternate measures, such as Bhutan’s Gross Domestic Happiness Index). Regardless of the exact formulation, there is tremendous utility in being able to communicate about the overall state of the nation, a concept that resonates with a broad, diverse set of audiences and potential users.

The Ocean Health Index has been developed with a similar endpoint in mind. Ocean health is an enormously complex topic; the index rolls into one number the condition of the many potential benefits we receive from the ocean. This singularity has strategic value for policymakers, managers, and the public in and of itself.

Are there downsides to generating a single number? Rolling lots of information into a single number masks a lot of detail. If people only pay attention to the single index score, then a lot of valuable information is lost about why a particular place received a particular score or what might be done to improve it. By our design, then, one can look under the hood of the single value to see the rich array of information regarding the ability of the ocean to deliver individual public goals. This more detailed information is available for those more interested in specific benefits or trade-offs among particular subsets of goals.

It’s hard to know if Kuznets would be happy with how his GDP measure altered the global landscape, but since he saw its power in his lifetime, it’s unlikely he would be surprised that it did. Economic and policy decisions require an understanding of both the big picture and the nature of the interactions and trade-offs among the component parts of that big picture. Ultimately, we hope that the Ocean Health Index can have a similar impact on decision-making and public understanding of how we interact with and benefit from the ocean.

The views expressed herein are those of the authors and do not necessarily reflect those of the National Oceanic and Atmospheric Administration or its agencies.

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