They fail to appreciate that even 30 or 40 individual companies provides less diversification than even one broad - market index fund. (moneysense.ca)
You have six to seven times less diversification in real life than the computer thought you had. (toolsformoney.com)
Keep in mind that this is a tall task, as the indices have hundreds of stocks in them and our model portfolios will only have a handful, which means less diversification overall. (financialcanadian.com)