Voluntary organisations in Wales account for just £1bn of the £45bn value of the UK-wide sector, according to data published today.
The finding is one of many insights about income, organisations, employment and volunteering in the Welsh not-for-profit sector contained on a new website.
The Wales Council for Voluntary Action commissioned Data Unit Wales to create a data hub at a cost of £15,000.
The hub, which is due to be launched at today's gofod3 voluntary sector event in Cardiff, pulls together statistics from sources such as the National Council for Voluntary Organisations' UK Civil Society Almanac 2017 and the Welsh government.
About one in 22 people in the UK live in Wales. That the region accounts for only £1 of every £45 generated by the voluntary sector suggests it contributes a disproportionately small amount.
Anna Nicholl, director of strategy and development at the WCVA, said she was shocked by the extent of the voluntary sector wealth gap between Wales and the rest of the UK.
Nicholl said a range of factors could be responsible, including a low level of funding from trusts and foundations and the fact that Wales included some of the poorest parts of Europe.
"The sector should be bigger," she said. "It has to up its game and we need to raise awareness of the inequality of funding.
"The sector also needs to be aware of alternative funding mechanisms and work more closely with the private sector."
Nicholl warned that Brexit could make matters worse. Wales is due to receive £2bn in EU structural fund investment from 2014 to 2020.
"The level of investment intended for Wales is significantly greater, on a per capita basis, than any other UK nation or region," she said. "We’re really concerned that Brexit will lead to a further weakening of the sector’s income in Wales."
The hub reveals that government funding accounted for 49 per cent of charity income in Wales in 2014/15, compared with 35 per cent for the UK overall. However, the proportion for Wales fell from 55 per cent in 2010/11.
Ruth Marks, chief executive of the WCVA, said the third sector in Wales was "operating with one hand tied behind its back".
She said: "The data hub shines a light on the real challenges we face, including government cuts, a post-Brexit world without EU funding and a failure by Welsh third sector organisations to capitalise on UK-wide funding."
Of 32,000 third sector organisations operating in Wales, 97 per cent of them are based in Wales only, and 20 per cent of those work in sports and recreation.
The hub reveals that more than one in four people aged 16 or over volunteer in some capacity in Wales, contributing £750m worth of time.