collect ideas and feedback on these issues. This paper should be considered work in progress and updated versions with more data and analyses will be published over the next months.

In this paper, we start by quantifying the number of people _exposed_ to extreme weather events globally today. We find that a 4.5 billion people are exposed to an extreme flood, drought, cyclone, or heatwave. Of those exposed, 2.3 billion are poor at the $6.85 poverty line (the median poverty line of upper middleincome countries) and 390 million are extremely poor at the $2.15 poverty line (the median poverty line of low-income countries).

Then, we identify the exposed households who are particularly _vulnerable_ and therefore _at high risk_ of experiencing severe economic impacts from these events. There are many determinants of vulnerability but we can broadly group determinants into two aspects: (i) the physical propensity to experience severe income, asset or health loss and (ii) the inability to cope with and recover from the losses through income or transfers (public and private). We use available data to provide some indicative estimates on these two aspects of vulnerability.

Physical propensity to experience severe losses is proxied using data on access to water and electricity. These are chosen to reflect the ability of a household to still access clean water in the face of lack of water availability or flood-contamination of water supplies, and the ability of households to access cooling appliances to cope with heatwaves.<sup>3</sup> However, more work on the right infrastructure indicators to use is needed and different dimensions of physical vulnerability are important for different types of shocks, for instance access to markets and emergency services, or coverage by early warning systems that help anticipate and mitigation impacts of extreme weather.

Inability to cope or recover is measured as not having income to manage the impact of a shock; not having education to switch livelihoods or access information and resources to recover; not having access to public support such as social protection; and not having access to financial services.

In structure the measure is similar to the World Bank’s multidimensional poverty measure (World Bank, 2018), although some of the dimensions considered are different and deprivations are counted just for those exposed to extreme weather events. In particular, we present the number of people highly vulnerable according to each separate indicator, and count the number of indicators according to which individuals can be considered highly vulnerable. A household is at high risk if it is exposed and highly vulnerable according to one or more dimensions.

The approach proposed is applicable to most countries. However, the data requirements are still intensive, as is the case with other multidimensional measures of household wellbeing. Each dimension captures an important aspect of vulnerability but reduces country coverage as not all surveys have all required measures. The dimensions chosen for the worked example in this paper were chosen because they had good coverage, but even then, the cost of adding each dimension in terms of coverage is clearly seen. Adding additional relevant dimensions – such as livelihoods or occupation or building quality – would make this challenge even larger and create a trade-off between coverage and comprehensiveness.

> 3 Having access to basic infrastructure services is not an absolute protection against natural disasters, in particular if these services are interrupted or disrupted during an extreme event. In some cases, access to these services can even backfire, for instance if piped water become contaminated after a storm. However, people with access to these services can still be considered as less vulnerable than people who do not have access to them.

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