The Water Price Index

To begin, we looked into the quality of tap water in each location, as it was important above all to see if and where the water was safe to drink. Next, we looked at the monthly consumption cost* of tap water in each city, from which we were able to calculate the percentage deviation from the median price for all the cities in the list. The results show more or less just how much citizens in each metropolis pay for their tap water compared to the rest of the world.

For the second part of the study, we turned our attention to bottled water. Despite negative effects on the environment, bottled water has become a ubiquitous phenomenon in many cities over recent decades, with prices varying greatly from place to place or among brands.

To determine exactly how much this varies, we found the price of a typical affordable bottle of water that a tourist may buy at a supermarket. We broke it down even further by looking at the average price per bottle of three of the most common water brands – Evian, Perrier/Nestlé and the local Coca Cola brand water in each city. Finally, we were able to average the cost of all these different brands to see which cities have the most expensive and cheapest bottled water, calculating the percentage deviation from the median price in the index.

The final index paints a picture of how the price of water varies worldwide, as well as giving an overview of the differences in local tap water costs and water stress levels found across the globe.

*The global average water consumption per person per month is 15 cubic square meters.

Instructions for journalists

The index is default ranked by the final column, showing the average deviation in price for bottled water in each city, ordered from highest to lowest. Each individual column can be filtered, and the full methodology explaining how each factor was evaluated can be found underneath the table.

International Results

** For Wellington, New Zealand, the cost of tap water is paid through a flat property rate that depends on the property type. This water pricing model is unique in the dataset and prevents a fair comparison with other locations. Data for “Tap Water Price” for Wellington, New Zealand is therefore omitted.

METHODOLOGY

The Water Price Index compares and analyses the costs of tap water and bottled water in 120 cities around the world, showing the actual average costs for consumption as well as the price percentage deviation from the dataset median in each location.

City Selection

The cities were selected due to their popularity as tourist destinations, with care taken to include locations that face a heightened risk of water shortage. A large number of metropolitan areas selected for analysis were taken from the key publications ‘Ranking Port Cities with High Exposure and Vulnerability to Climate Extremes’ – OECD (2008) and the ‘Sustainable Cities Water Index’ – Arcadis (2016). Additional research into media reports on water shortages was used to source locations not covered in these publications.

To reflect this, a water stress category was included for each city in the table, representing the ratio of total water consumption to supply. Higher values indicate more competition among users (Source: WRI Aqueduct 2019).

Factors

The index is divided into two sections with multiple factors that measure the costs for tap water and bottled water in each city:

Tap Water:

• Tap Water Quality (Score)
• Tap Water Price (GBP/m3) up to 15m3 per month
• Tap Water Price (Deviation from Median)

Bottled Water:

• Typical Affordable Bottle 500 ml, Price (GBP)
• Evian 500 ml, Price (GBP)
• Perrier / Nestlé 500 ml, Price (GBP)
• Local Coca-Cola Water Brand 500 ml, Price (GBP)
• Bottled Water, Price (Average Deviation from Median)

Calculation of Price Deviations

In order to provide some relative context to the prices, the deviation of prices from the dataset median – the midpoint of the dataset – for both tap and bottled water are included. The deviation from the median is calculated using the following formula:

For “Tap Water Price (Deviation from Median)”, the price deviation is calculated from a single factor.

For “Bottled Water, Price (Average Deviation from Median)”, the percentage reflects the average of all price deviations calculated from each category of bottled water.

TAP WATER

Tap Water Quality (Score)

The quality of drinking water with regards to safety and public perception. Safety indicators include water, sanitation and hygiene (‘WASH’) data from international monitors such as UNICEF which analyse the national coverage of water access considered ‘free from contamination’. Other safety indicators from the World Health Organisation provide national scores for water safety based on the number of DALY rates (age-standardised, disability-adjusted life years lost per 100,000 persons) due to exposure to unsafe drinking water. Additionally, data on public perception of the quality of water was taken at the local level from self-reported survey results on pollution perceptions.

The final score is a combination of the following indicators:

• The 2020 Environmental Performance Index (EPI) measurement of ‘unsafe drinking water’ (country level).
• WHO/UNICEF Joint Monitoring Programme for Water Supply, Sanitation and Hygiene (JMP) data on the ‘Basic and Safely managed Drinking Water Coverage’. 2017 values were taken for ‘proportion of population using improved water supplies’ and ‘free from contamination’. Figures taken for ‘urban areas’, where possible, otherwise ‘national’ figures were used (country level).
• Numbeo Pollution Index for Drinking Water Pollution and Inaccessibility indicators (city-level).

Sources: The Yale Center for Environmental Law & Policy 2020 Environmental Performance Index (EPI), WHO/UNICEF Joint Monitoring Programme for Water Supply, Sanitation and Hygiene (JMP), Numbeo.

Tap Water Price (GBP/m3) up to 15m3 per month

The factor displays the billing price per month for 1 m3 of tap water based on the latest effective tariff from the The International Benchmarking Network for Water and Sanitation Utilities (IBNET) database. Each city is represented by one utility provider and their respective rates. A list of the cities and their utility providers can be supplied upon request.

To calculate the monthly price/m3, the following parameters were used:

• Service type: Water, or Water and Wastewater where the same price applies for both.
• Latest available water tariff (based on consuming up to 15 m3 of water per month).
• Additional monthly service charges where applicable.
• VAT where applicable.

Source: IBNET.

Tap Water Price (Deviation from Median)

The deviation of tap water price from the dataset midpoint, as described in “Calculation of Price Deviations” above. This factor represents how much more or less citizens in each city pay for tap water compared to the median price in the index.

BOTTLED WATER

This section compares the price for bottled water from up to two different supermarket outlets in each city. Supermarkets were chosen according to their market share and the online availability of their prices. The intention was to create a sample of representative, local supermarkets. On rare occasions, special outlets for beverages or online only supermarkets were taken into account to complete the samples.

All prices were taken at full price without discount. The bottle size for each profile was standardised to 500 ml to ensure comparability. If this specific size didn’t exist, the bottle size closest to this profile was chosen (e.g. 330 ml, or 750 ml). The price collection was carried out between January and February 2021.

Full details for the names of the supermarkets and/or water profiles are available upon request.

Typical Affordable Bottle 500 ml, Price (GBP)

The cost of an affordably-priced 500 ml bottle of still water bought at a supermarket in each city. Typical was defined as the brand with the most variants available at supermarkets in each location.

Evian 500 ml, Price (GBP)

The average cost for a 500 ml bottle of Evian-brand still water in each city.

Perrier / Nestlé 500 ml, Price (GBP)

The average cost for a 500 ml bottle of Perrier-brand sparkling water in each city. On rare occasions where Perrier was not available in a location, San Pellegrino (also a Nestlé brand) was chosen instead.

Local Coca-Cola Water Brand 500 ml, Price (GBP)

The average cost for a 500 ml bottle of still water produced by the local Coca-Cola company brand present (e. G. Dasani) in each city.

Bottled Water, Price (Average Deviation from Median)

The average deviation of bottled water price from the dataset midpoint, as described in “Calculation of Price Deviations” above. This factor represents how much more or less people in each city pay for bottled water compared to the median price in the index.

The Average Price deviation is based on the price deviations for all categories of bottled water (“Typical”, “Perrier”, “Evian”, “Coca-Cola’s local water brand”) as well as the additional profiles “most affordable” and “Pepsi-Cola’s local water brand”.

Currency conversion correct as of average of conversion rates between 08.01.2021 – 08.02.2021.