Individual Savings Accounts are undergoing some changes
The proportion of female savers and young people turning to Isas has been accelerating since the tax-free scheme was launched, research suggests.
Individual Savings Accounts (Isas) were introduced 10 years ago by Gordon Brown in an attempt to encourage UK residents to get into the savings habit.
A report by the Halifax suggests that the number of women with an Isa grew by 52% in the first seven years.
Isas were increasing popular with under 25s saving for a mortgage deposit.
Isas were brought in by Mr Brown at the time when he was chancellor, and proved popular with savers.
Some 37% of households in the UK have an Isa, according to the research - which draws on data from the Bank of England, HM Revenue and Customs, and the Department for Work and Pensions.
This total rose by 53% to 14.2 million in the nine years to March 2009, said the research by the Halifax, which is now part of Lloyds Banking Group.
The effect of the latest downturn might be among the reasons for the fall in the average amount paid into each account. This dropped to £2,636 in 2008-09, down from £3,064 in 1999-00.
Slightly more men than women signed up to a tax-free account in the first seven years of the scheme, the latest available data showed.
However, the number of women registering accelerated - with the number rising by 52% over the same period compared with a 35% rise among men. The research does not offer any theory as to why this trend had occurred.
The lifestyles of young people could explain the trends in take-up of Isas among the younger generation. Those under 25 have seen the fastest rise in those registering - up 88% in the first nine years of Isas.
However, this age group - often facing student debts - still has the lowest number of individuals subscribing to an Isa.
Many in this age group could be saving for a deposit on a home, whereas first-time buyers in the 25-to-34 age bracket could explain why that age group saw the smallest rise in take-up (24%).
On a national and regional level, the proportion of households with an Isa was highest in the south east of England, but the number has been growing the fastest in Scotland, the research found.
Each person is only allowed to open one cash and one stocks and shares Isa each year, with the same or different providers. Cash has become the most popular component, according to the Halifax research.
The amount people can save in an Isa is rising from £7,200 to £10,200, of which half can be saved in cash and half, or all, in stocks and shares.
The new limit came into force in October 2009 for anyone born on or before 5 April, 1960. For everyone else the limit will rise from 6 April, 2010.
The changes were announced because in low-interest times, the government wanted more reward for those who have saved.
However, a survey by National Savings and Investments (NS&I) found that only 15% of those asked understood the new limits.
"Understanding the allowances and reviewing the terms of the product is vital for savers," said John Prout, sales director at NS&I.
"With less than two months to go until the end of the tax year, there is no time like the present for everyone to check their finances and plan to benefit from tax-free savings."