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Understanding differences between S&P500 index-tracking ETFs
Regarding SPY: "One SPDR unit is valued at approximately 1/10 of the value of the S&P 500. Dividends are distributed quarterly, and are based on the accumulated stock dividends held in trust, less any expenses of the trust."  (source)  These are depository receipts, not the actual stocks. Regarding IVV: "The component stocks are weighted according to the total float-adjusted market value of their outstanding shares. The Fund invests in sectors, such as energy, information technology, industrials, financials, consumer staples, healthcare, telecom services, consumer discretionary and materials."  (more here) VOO is the Vanguard S&P 500 ETF. The tracking error seems pretty small to me.  I went to Google Finance and plotted the percent change for all four on one chart.  They lie pretty much on top of one another.  The actual dollar value of each one doesn't matter nearly as much as the fact that they move up and down almost in lock-step.  There may be a larger difference going farther out, but for three separate financial products, the agreement is still remarkably good.