Some investments do not need a complicated thesis.
The iShares S&P 500 AUD ETF (ASX: IVV) gives Australian investors access to many of America's largest companies through a single ASX-listed fund.
For me, that makes it a strong long-term option.
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Access to some of the world's strongest businesses
The IVV ETF tracks the S&P 500 Index, which contains around 500 large US companies, including Apple, Microsoft, Nvidia, Bank Of America, Walmart, Merck & Co, and Verizon.
That gives investors exposure to businesses operating across technology, healthcare, financial services, consumer products, industrials, communication services, and many other areas of the US economy.
I think this is particularly valuable for Australian investors. The ASX has some excellent companies, but our market is heavily influenced by financial and resources businesses. The US market gives investors much greater exposure to areas such as software, semiconductors, digital advertising, medical technology, and global consumer brands.
Many of the companies inside the S&P 500 also generate revenue around the world.
So while the IVV ETF invests in US-listed companies, the underlying businesses can have customers spread across North America, Europe, Asia, and other major markets.
That gives investors exposure to far more than the US economy alone.
The index can evolve over time
Another reason I like the IVV ETF is that ASX investors do not have to predict which companies will dominate the next decade.
The S&P 500 index changes as corporate America changes.
Companies that grow can become increasingly important within the index, while businesses that lose relevance can eventually become smaller holdings or leave the index entirely. For example, today Nvidia is highly important, whereas 50 years ago it was IBM.
I think that is a powerful feature for a long-term investor.
Twenty years from now, some of today's leading businesses may still be enormous. Others may have been overtaken by companies that are only beginning their growth stories today.
An investor in the IVV ETF does not need to identify those winners in advance.
They can simply continue owning a large collection of leading US businesses as the market develops.
It keeps investing simple
The IVV ETF also suits ASX investors who do not want to spend their spare time reading annual reports and comparing individual companies.
Buying individual shares can be rewarding, but it requires research and comes with the possibility of getting a company-specific decision badly wrong.
With the IVV ETF, one investment spreads money across hundreds of businesses.
That can make it easier to keep contributing through strong markets, weak markets, recessions, and whatever else happens over a long investing career.
For me, this simplicity is one of the fund's biggest strengths.
A sensible investment strategy that someone can stick with for decades can be far more powerful than a clever strategy they abandon after a difficult year.
There are still risks
The IVV ETF is diversified across hundreds of companies, but it is not immune from large falls.
US shares can become expensive, recessions can hurt corporate earnings, and the index can experience lengthy periods of weak performance.
The largest US companies also account for a meaningful share of the S&P 500 index, so the fund can become quite concentrated at the top.
Australian investors also have currency exposure because the IVV ETF is not hedged back to the Australian dollar. Movements in the Australian dollar against the US dollar can therefore influence returns.
Nevertheless, I would be comfortable accepting those risks with a long enough timeframe.
Foolish takeaway
I think the IVV ETF offers one of the simplest ways for ASX investors to participate in the long-term growth of major global businesses.
There will inevitably be periods when US shares fall out of favour, and I would expect plenty of volatility over the years.
But if I wanted an investment I could keep adding to and potentially hold for decades, the IVV ETF would be high on my list.
