Figures from the Centre for Economics and Business Research (CEBR), published tomorrow, suggest that the number of millionaires in Britain — 376,000 today — will nearly double to 690,000 by 2010.

By 2020, it says, the number of millionaires will reach 1.7m, more than four times the present level, and by then, 53% of them will be women, up from 40% now. The figures are based on “marketable” wealth, as defined by Revenue & Customs. This includes the value of housing, less mortgages, plus investments, savings and pensions.

The latest Revenue & Customs estimates, for 2003, show that there were 230,000 millionaires that year. But Jaspreet Sehmi, a CEBR economist, calculates that the stock-market rise, combined with increases in house values, has created nearly 150,000 new millionaires since then.

Between now and 2020 the CEBR expects a continued rise in the stock market and a 71% surge in house prices, increasing in line with average earnings plus a premium for the rising population and continued housing shortages.

Women will be beneficiaries of this growing wealth, it says, because of increasingly generous divorce settlements and the likelihood that they will outlive husbands. But more women are also becoming millionaires in their own right.

Although they are now in a minority when it comes to millionaire status, official figures show that they are knocking firmly on the door. The latest data reveal that 52% of those with a marketable wealth of between £500,000 and £1m were women.

However, women are well behind among the ranks of the super-rich. The Sunday Times Rich List 2006 revealed that only 77 of the richest 1,000 people in Britain are women. The combined wealth of the richest 100 women was £29.4 billion, led by Tina Green, wife of the retailing billionaire Sir Philip Green, with £4.9 billion.

Just over a third of Britain’s millionaires are over the age of 65, with 45% in the 45-64 age bracket. Millionaires have an average age of 56. That has increased in recent years as the “baby boomers” have got older.

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