The topline figure includes spa facility revenues of US$77.6bn (€71.1bn, £63.4bn) as well as the associations and education, consulting, media and event sectors that support spas, which are valued at US$21bn (€19.2bn, £17.2bn).

And while worldwide spa revenues increased by a modest 2.3 per cent from 2013 to 2015, researchers at the Global Wellness Institute (GWI) – the organisation behind the report – says this is largely due to the US dollar currency conversion from large spa markets across Europe and Asia. If global spa facility revenues are converted to the euro instead, the market actually grew at a robust 25 per cent.

Spa locations worldwide jumped from 105,591 in 2013 to 121,595 in 2015 – meaning the industry has added just over 16,000 spas, more than 230,000 workers (to reach 2.1m) and US$3.5bn (€3.2bn, £2.9bn) in revenue.

These figures from the spa sector feed into the wider international wellness market which the GWI estimates is now a US$3.72 trillion (€3.4tn, £3tn) industry, a number which has increased by 10.6 per cent since 2013.

“Recent years have been marked by global economic contraction and disruptive geopolitical events, but a ‘wellness economy’ just keeps rising, with an upward trajectory that seems unstoppable,” says GWI senior research fellow Ophelia Yeung.

Yeung pointed to ‘megatrends’ of an emerging global middle class, a rapidly ageing population, increase in chronic disease and stress, the failure of the ‘sick-care’ medical model, and a growing subset of more affluent, educated consumers “seeking experiences rooted in meaning, purpose, authenticity and nature”, as fuelling the growth in the market.

Revenue-earning thermal and mineral springs added 660 facilities across 109 countries between 2013 and 2015, earning US$51bn (€46.7bn, £42bn) in 2015, up 2 per cent from 2013. The GWI said that while these gains look modest, its research finds rapidly rising consumer interest in springs-based activities – and similarly, 2015 revenues are also heavily impacted by the depreciation of European currencies against the dollar.

Wellness tourism grew 14 per cent in the same two-year period – more than twice as fast as overall tourism expenditures. World travellers made 691 million wellness trips in 2015.

Wellness real estate – which includes residential, hospitality and mixed-use developments incorporating wellness – was one of the fastest-growing sectors, up 19 per cent to US$118.6bn (€108.6bn, £97bn) in 2015.

Other subsets measured in the report include beauty and anti-ageing; workplace wellness; fitness and mind-body; healthy eating, nutrition and weight loss; preventative and personalised medicine and public health; and complementary and alternative medicine.

* The preliminary figures were unveiled at the Global Wellness Summit in late October, ahead of the full research which will be released in January. Turn to p80 to read about the summit in more depth.