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The economics of ‘greeniums’ in sustainable finance: doing good has a price

Sustainability has become one of the most pressing issues facing society. Patterns of human production and consumption have become unsustainable. On the environmental front, climate change, land-use change, biodiversity loss and depletion of natural resource are destabilising the Earth’s eco-system.

Furthermore, data on poverty, hunger and lack of healthcare show that many people live below minimum social standards. This has led to greater emphasis being placed on sustainable development: ‘development that meets the needs of the present without compromising the ability of future generations to meet their own needs’ (The Brundtland Report, 1987: Ch.2, para. 1).

The financial system has an important role to play in channelling capital in a more sustainable way. Since current models of finance do not consider the welfare of future generations in investment decisions, sustainable finance has been developed to analyse how investment and lending decisions can manage the trade-off inherent in sustainable development: sacrificing return today to enhance the welfare of future generations.

However, some commentators argue that such trade-offs are not required. They suggest that investors can ‘do well by doing good’. In this blog, I will use ‘green’ bonds (debt instruments which finance projects or activities with positive environmental and social impacts) to explain the economics underpinning sustainable finance and show that doing good has a price that sustainable investors need to be prepared to pay.

I will analyse why investors might not be doing so and point to changes which may be required to ensure financial markets channel capital in a way consistent with sustainable development.

The growth of sustainable finance

Sustainable finance has grown rapidly over the past decade as concerns about climate change have intensified. A significant element of this growth has been in global debt markets.

Figure 1 illustrates the rapid growth in the issuance of sustainability-linked debt instruments since 2012. While issuance fell in 2022 due to concerns about rising inflation and interest rates reducing the real return of fixed-income debt securities, it rebounded in 2023 and is on course for record levels in 2024. (Click here for a PowerPoint.)

Green bonds are an asset class within sustainability-linked debt. Such bonds focus on financing projects or activities with positive environmental and social impacts. They are typically classified as ‘use-of-proceeds’ or asset-linked bonds, meaning that the proceeds raised from their issuance are earmarked for green projects, such as renewable energy, clean transportation, and sustainable agriculture. Such bonds should be attractive to investors who want a financial return but also want to finance investments with a positive environmental and/or social impact.

One common complaint from commentators and investors is the ‘greenium’ – the price premium investors pay for green bonds over conventional ones. This premium reduces the borrowing costs of the issuers (the ‘counterparties’) compared to those of conventional counterparties. This produces a yield advantage for issuers of green bonds (price and yield have a negative relationship), reducing their borrowing costs compared to issuers of conventional bonds.

An analysis by Amundi in 2023 using data from Bloomberg estimated that the average difference in yield in developed markets was –2.2 basis points (–0.022 percentage points) and the average in emerging markets was –5.6 basis points (–0.056 percentage points). Commentators and investors suggest that the premium is a scarcity issue and once there are sufficient green bonds, the premium over non-sustainable bonds should disappear.

However, from an economics perspective, such interpretations of the greenium ignore some fundamentals of economic valuation and the incentives and penalties through which financial markets will help facilitate more sustainable development. Without the price premium, investors could buy sustainable debt at the same price as unsustainable debt, earn the same financial return (yield) but also achieve environmental and social benefits for future generations too. Re-read that sentence and if it sounds too good to be true, it’s because it is too good to be true.

‘There is no such thing as a free lunch’

In theory, markets are institutional arrangements where demand and supply decisions produce price signals which show where resources are used most productively. Financial markets involve the allocation of financial capital. Traditional economic models of finance ignore sustainability when appraising investment decisions around the allocation of capital. Consequently, such allocations do not tend to be consistent with sustainable development.

In contrast, economic models of sustainable finance do incorporate such impacts of investment decisions and they will be reflected in the valuation, and hence pricing, of financial instruments. Investors, responding to the pricing signals will reallocate capital in a more sustainable manner.

Let’s trace the process. In models of sustainable finance, financial instruments such as green bonds funding investments with positive environmental impacts (such as renewable energy) should be valued more, while instruments funding investments with negative environmental impacts (such as fossil fuels) should be valued less. The prices of the green bonds financing renewable energy projects should rise while the prices of conventional bonds financing fossil-fuel companies should fall.

As this happens, the yield on the green bonds falls, lowering the cost of capital for renewable-energy projects, while yields on the bonds financing fossil-fuel projects rise, ceteris paribus. As with any market, these differential prices act as signals as to where resources should be allocated. In this case, the signals should result in an allocation consistent with sustainable development.

The fundamental point in this economic valuation is that sustainable investors should accept a trade-off. They should pay a premium and receive a lower rate of financial return (yield) for green bonds compared to conventional ones. The difference in price (the greenium), and hence yield, represents the return investors are prepared to sacrifice to improve future generations’ welfare. Investors cannot expect to have the additional welfare benefit for future generations reflected in the return they receive today. That would be double counting. The benefit will accrue to future generations.

A neat way to trace the sacrifice sustainable investors are prepared to make in order to enhance the welfare of future generations is to plot the differences in yields between green bonds and their comparable conventional counterparts. The German government has issued a series of ‘twin’ bonds in recent years. These twins are identical in every respect (coupon, face value, credit risk) except that the proceeds from one will be used for ‘green’ projects only.

Figure 2 shows the difference in yields on a ‘green bond’ and its conventional counterpart, both maturing on 15/8/2050, between June 2021 and July 2024. The yield on the green bond is lower – on average about 2.2 basis points (0.022 percentage points) over the period. This represents the sacrifice in financial return that investors are prepared to trade off for higher environmental and social welfare in the future. (Click here for a PowerPoint.)

The yield spread fluctuates through time, reflecting changing perceptions of environmental concerns and hence the changing value that sustainable investors attach to future generations. The spread tends to widen when there are heightened environmental concerns and to narrow when such concerns are not in the news. For example, the spread on the twin German bonds reached a maximum of 0.045 percentage points in November 2021. This coincided with the 26th UN Climate Change Conference of the Parties (COP26) in Glasgow. The spread has narrowed significantly since early 2022 as rising interest rates and falling real rates of return on bonds in the near-term seem to have dominated investors’ concerns.

These data suggest that, rather than being too large, the greeniums are too small. The spreads suggest that markets in debt instruments do not seem to attach much value to future generations. The valuation, price and yield of green bonds are not significantly different from their conventional counterparts. This narrow gap indicates insufficient reward for better sustainability impact and little penalty for worse sustainability impact.

This pattern is repeated across financial markets and does not seem to be stimulating the necessary investment to achieve sustainable development. An estimate of the scale of the deficit in green financing is provided by Bloomberg NEF (2024). While global spending on the green energy transition reached $1.8 trillion in 2023, Bloomberg estimates that $4.8 trillion needs to be invested every year for the remainder of this decade if the world is to remain on track under the ‘net zero’ scenario. Investors do not seem to be prepared to accept the trade-off needed to provide the necessary funds.

Can financial markets deliver sustainable development?

Ultimately, the hope is that all financial instruments will be sustainable. In order to achieve that, access to finance would require all investors to incorporate the welfare of future generations in their investment decisions and accept sacrificing sufficient short-term financial return to ensure long-term sustainable development. Unfortunately, the pricing of green bonds suggests that investors are not prepared to accept the trade-off. This restricts the ability of financial markets to deliver an allocation of resources consistent with sustainable development.

There are several reasons why financial markets may not be valuing the welfare of future generations fully.

  • Bounded rationality means that it is difficult for sustainable investors to assign precise values to future and distant benefits.
  • There are no standardised sustainability metrics available. This produces great uncertainty in the valuation of future welfare.
  • Investors also exhibit cognitive biases, which means they may not value the welfare of future generations properly. These include present bias (favouring immediate rewards) and hyperbolic discounting (valuing the near future more than the distant future).
  • Economic models of financial valuation use discount rates to assess the value of future benefits. Higher discount rates reduce the perceived value of benefits occurring in the distant future. As a result, long-term impacts (such as environmental conservation) may be undervalued.
  • There may be large numbers of investors who are only interested in financial returns and so do not consider the welfare of future generations in their investment decisions.

Consequently, investors need to be educated about the extent of trade-offs required to achieve the necessary investments in sustainable development. Furthermore, practical models which better reflect the welfare of future generations in investment decisions need to be employed. However, challenges persist in fully accounting for future generations and it may need regulatory frameworks to provide appropriate incentives for effective sustainable investment.

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Questions

  1. Using demand and supply analysis, illustrate and explain the impact of sustainable investing on the markets for (i) green bonds and (ii) conventional bonds. Highlight how this should produce an allocation of finance capital consistent with sustainable development.
  2. Research the yields on the twin bonds issued by Germany since this blog was published. Can you identify any association between heightened environmental concerns and the spread between the ‘green’ and conventional bond?
  3. Analyse the issues which prevent financial markets from producing the pricing signals which produce an allocation of resources consistent with sustainable development.
  4. Research some potential regulatory policies which may provide appropriate incentives for sustainable investment.