The stock market is riskier and more volatile than it was in past decades. Here's why.

• The S&P 500 has become more volatile in recent years, according to research firm DataTrek.
• That's partly to do with bad luck and partly to do with unexpected events impacting the market. 
• The bigger factor is the massive growth of big tech stocks that make up more and more of the S&P 500.

Stocks are a risky investment, but huge intraday swings and relentless volatility seem to have only grown more frequent and intense in recent years. 

There are a number of factors that seem to have amplified volatility in large cap stocks, but according to DataTrek, the gains haven't necessarily increased in tandem with the risk.