There was also a significant shortfall in what people needed to survive on and what benefits were available.
An average family needed $683 per week to make up for a main income earner not being able to bring in money because of sickness.
But for a family with dependent children the maximum benefit was $340 per week for a job seeker allowance (previously known as the sickness benefit).
More than half of those questioned (51 per cent) did not know that if the main earners' partner received $30,000 or more a year they might receive only part or none of the benefit.
Income protection insurance for a family of four with a combined income of $100,000 costs about $25 a week. This includes a month's standown but if this was extended out the premium could be as low as $12 a week.
Peter Neilson, chief executive of the Financial Services Council, said its research showed people underestimated the value of their income and the chances of being off sick for a long time.
When asked what their biggest asset was 45 per cent said it was their home.
Yet a salary of $50,000 or more was worth $2 million over a 40 year working life, he said.
Of those surveyed 60 per cent thought they had the same or greater likelihood of being off work long-term following an accident rather than after sickness.
But working age Kiwis were 1.8 times more likely to be off work for six months or more from sickness than an accident, according to the council.
Over the last five years only one in eight of the households struck with long term illness had income protection insurance in place when it happened.
Neilson said the income gap following sickness needed filling and income protection insurance was one of the means of doing so.
The forum will also feature speakers from the Cancer Society, Stroke and Heart Foundations as well as people who have lost their incomes due to ill health.
Figures on the long-term sickness income gap.