According to new research from Saga Share Direct, one in three have bought shares in a company to help fund their retirement.
Other common reasons the over 50s buy and sell company shares are to give them a regular source of income and because they think they will get a higher return by investing in shares than if they leave their money in a savings account.
Some said they like to keep a close eye on the FTSE 100 as a hobby and others say they have bought shares because they like numbers and because trading shares helps keep them mentally active.
Saga estimates that around 11 million over 50s own shares but not everyone has bought them.
One in 13 people have inherited them from a family member and kept them and the same number of people said they acquired the shares they own through a generous employer.
It appears the older you get the more likely you are to own shares as almost three fifths of people aged 80 to 89 said they have bought shares over their lifetime.
Men are most likely to take an interest in the stock market, as three quarters said they have bought shares.
This is compared to three fifths of women.
Women were found to be more likely to inherit shares than men.
With people living longer in retirement, it makes sense to take steps which could boost your income in later life.
Investing in the stock market can be risky though, and investing in individual company shares is riskier than investing in a portfolio of collective investment funds.
Some of the non-financial reasons for owning company shares uncovered in this research were interesting.
Keeping our brains active in later life is a positive step, so investing in company shares to stay engaged with the numbers and follow market news is a smart idea.
Our local U3A has an investments and money matters group which meets regularly to share information about financial matters.
This could be a good way to take an active interest in stock market investments in retirement, without necessarily diving straight in and trading shares with money you might not be able to afford to lose.