In the span of one small year, the tax-free savings account has ballooned in popularity.

The amount of money in TFSAs swelled by 27 per cent in the final six months of last year, and while most assets are still sitting in savings accounts at retail banks, growth at full-service brokerage accounts is accelerating.

According to a report that Toronto-based financial research firm Investor Economics will publish, Canadians opened 4.7 million TFSA accounts by the end of December, 2009, containing assets of $15.8-billion. That includes the 3.6 million accounts holding $12.4-billion that sprang up from January to the end of June of last year.

There are about 27 million Canadians over the age of 18, which suggests roughly one in five people who are eligible to open a TFSA have done so.

Judith Cane is in Vancouver, partying in skiers plaza, thanks to her TSFA. The 53-year-ancient Ottawa independent financial adviser opened her account in January of 2009 and made roughly 8 per cent by investing in mutual funds. She used the money from her TSFA to pay for her family’s holiday to the Winter Olympics.

“We use mine for special vacations, like this trip,” Ms. Cane said. The money going into her husband’s TFSA will be used to supplement their son’s registered retirement savings plot.

Most of the TFSA funds – $11.9-billion – are invested with retail banks, the Investor Economics data shows. But TSFA assets with full service brokerages and online discount brokerages are growing quick, closing the year at $1.7-billion and $1.4-billion, respectively.

At the end of 2009, the average amount held in each TSFA was $3,400. The average assets for accounts opened with retail banks were on the low end of the scale at $3,170 while the average among full-service brokerage accounts were on the high end at $5,240.

Carlos Cardone, a senior consultant at Investor Economics, says most of the TSFA money at the retail banks is sitting in savings accounts and GICs. The funds held by full service brokerages are likely invested in market-sensitive instruments like equities, bonds, and funds.

Jamie Golombek, managing director of tax and estate plotting at CIBC Private Wealth Management, says the take-up rate for TFSAs is still disappointingly low. “I reckon that over the next number of years, the entire financial plotting situation will change and Canadians will start directing all of their savings to TFSAs, to the extent that they are able.”