Five companies have become the pillars of the stock market in 2017, and their names shouldn't sound unfamiliar, either. Apple, Alphabet, Microsoft, Amazon and Facebook are carrying a load of weight on their shoulders.
As the Nasdaq hit a record high Thursday, it's important to note that the top five S&P 500 stocks by market capitalization represent 12 to 13 percent of the index's overall weight, and all of them — technology-related stocks — are trading in positive territory year to date.
Apple, maker of the iPhone, is up 23 percent year to date, Google's parent company Alphabet is up 9 percent, Windows operator Microsoft has climbed 6 percent, e-commerce giant Amazon has risen 20 percent and social media darling Facebook is up a whopping 25 percent, as of Thursday's close.
If you haven't already, it's worth noting that Apple, Facebook and Amazon have already climbed at least 20 percent for the year, and this is one of the reasons the stock market is holding up so well.
To date, the S&P 500 index is trading well above its 200-day moving average.
From this perspective, things might look healthy for equities. But about 120 to 130 stocks in the index are actually trading below that moving-day average. So, those five above-mentioned stocks are doing a lot of the heavy lifting.
Hence the record highs in the market of late, despite not every company performing at par.
— CNBC's Lauren Thomas contributed to this report.