With the at a historic high, it's time to review the many ways you can own this important index.
Why should you own it? Because it is a "core" holding of any stock market portfolio. If you want to own a broad swath of the market, this is where you start.
Thanks to exchange-traded funds (ETFs), you can buy the S&P 500 from several companies at a low cost, and in many different forms.
Start with the S&P 500 itself. All three large ETF families (State Street, iShares and Vanguard) offer it for sale. The SPDR S&P 500 (SPY), the Vanguard 500 Index (VOO) and the iShares Core S&P 500 (IVV) all track the S&P 500 and offer very low expenses: 0.07 percent in the case of IVV, 0.09 percent for the SPY, and 0.05 percent for the VOO.
But there are plenty of other ways to slice and dice ownership of this big-cap index. One of the most popular is the Rydex S&P Equal Weighted Index (RSP). Here, you abandon the idea of the S&P as a market-cap-weighted index (the biggest stocks get a bigger weighting) and instead all 500 stocks have the same weighting.
What this means is that you get proportionally greater exposure to the more "mid-cap" names in the S&P 500, since every stock is assigned the same weighting (0.2 percent of the fund). So the biggest stock by market cap, Apple (AAPL), with a $458 billion market cap, would have the same weight as, say, Union Pacific, with a $70 billion market cap.
This strategy has worked this year...the RSP is up 46 percent, vs. 22 percent for the S&P 500.
There's plenty of other strategies. For example, you may want to own a portion of the S&P that is less volatilethan the rest of the index. The PowerShares S&P 500 Low Volatility ETF (SPLV) consists of the 100 stocks in the S&P 500 with the lowest volatility, which consists mostly of consumer names like Johnson & Johnson (JNJ), Kellogg (K), and Pepsi (PEP).
You can go in the opposite direction--you can own the most volatile stocks in the S&P through the S&P 500 High Beta Portfolio (SPHB), which owns the 100 stocks in the S&P with the highest beta, or sensitivity to market movement.
So, for example, if the S&P were up 1.0 percent, these names would typically be up more than 1 percent. You will find a lot of tech and financials on this list.
Owning high-beta names has been a successful strategy this year: the SPHB is up 29 percent, versus 16 percent for the SPLV and 22 percent for the S&P 500.
There's also the old standy of investing in value or growth. The iShares S&P 500 Growth Index (IVW) invests in the faster-growing half of the S&P 500, while the S&P 500 Value Index (IVE) invests in the slower-growing half.
You might think that companies are defined as growth companies if they grow their earnings faster than their value counterparts, but it's a little more complicated than that. Several different metrics are used, including price momentum, earnings per share, and sales per share, as well as price to book, price to sales, and price to earnings; S&P then ranks each stock by the ratio of its growth score to its value score.
The companies in these ETFs can change overtime. Right now, you will find a lot of tech (Apple, Google, Microsoft) and healthcare (Merck, Johnson & Johnson) names in the Growth ETF, and a lot of financial names (Berkshire Hathaway, JP Morgan, Citigroup) in the Value ETF.
So far this year, it's a wash: the Growth and Value ETFs are both up 22 percent. However, over the very long term, most investors would say that value has outperformed growth.
—By CNBC's Bob Pisani