Are We in a Bubble? A Look at the Australian and US Equity Markets in 2025

Written by Steve Landers

As we approach the final quarter of 2025, equity markets in both Australia and the United States have delivered strong returns, driven by monetary easing, resilient earnings, and a wave of optimism around artificial intelligence. But beneath the surface, questions are mounting: Are these markets overvalued? Are we in a bubble? And how sustainable is the AI-driven rally?

Let’s unpack the data and trends to help everyday investors make sense of what’s happening.

Australian Equity Market: Valuations and Earnings

The S&P/ASX 200 has returned +7.5% over the last 12mths, buoyed by easing inflation, resilient corporate earnings, and strong consumer spending. The banking sector has led the charge, with Westpac up over 19% and Commonwealth Bank and ANZ up nearly 17%.

However, concerns are emerging around valuation multiples. According to Schroders, Australian equity valuations are increasingly disconnected from fundamentals, with price-to-earnings (PE) ratios well above long-term averages. The tech sector, in particular, is trading at elevated levels, driven more by sentiment than earnings.

Key Observations:

  • Financials are driving index performance.

  • Materials and midcap companies remain arguably undervalued.

  • Valuation multiples are stretched, especially in tech.

  • Earnings growth is solid but concentrated in a few sectors.

Bubble Risk? Moderate.

While valuations are elevated, they are not uniformly excessive. The market is supported by earnings in key sectors, but sentiment-driven tech valuations warrant caution.

US Equity Market: Valuations and Earnings

The S&P 500 has rallied neary 435% from April lows, hitting all-time highs this year. Corporate earnings are strong, with profits projected to grow 10% year-over-year. However, valuations are flashing warning signs: [bilello.blog]

  • PE ratio for the S&P 500 is 27.9, over 60% above the historical median.

  • Price-to-sales ratio is at a record 3.3x, the highest in history.

  • The Buffett Indicator (market cap to GDP) stands at 217%, a level historically associated with bubbles. [finance-monthly.com]

Morningstar reports nearly 40% of market cap is concentrated in just 10 mega-cap stocks tied to AI. This concentration increases systemic risk if AI growth falters. [morningstar.com]

Key Observations:

  • Mega-cap tech dominates market performance.

  • Valuations are historically high.

  • Small-cap and value stocks remain undervalued.

  • Earnings growth is robust but unevenly distributed.

Bubble Risk? Elevated.

The US market shows classic signs of speculative excess, particularly in AI-linked stocks. While earnings are strong, valuations leave little margin for error.

AI Monetisation: Hype or Reality?

AI is no longer just a buzzword—it’s a revenue driver.

  • During Morgan Stanley’s 2025 conference, companies across sectors spoke of their optimistic about their prospects to monetise AI investment. Corporate leader’s optimism lies in the potential to aid in cost reduction: [morganstanley.com]

  • Microsoft’s AI business is expected to hit $10 billion in annual revenue. [globalxetfs.com]

  • OpenAI and Anthropic are generating billions in revenue from generative AI platforms.

AI is helping firms reduce costs, improve customer service, and optimise operations. However, many AI stocks trade at extreme valuations—Nvidia at 57x earnings, Arm Holdings at 90x—raising concerns about sustainability. [finance-monthly.com]

Key Observations:

  • AI is delivering real returns, especially in cloud, semiconductors, and software.

  • Monetisation is accelerating, but uneven.

  • Valuations in AI stocks are speculative and vulnerable to sentiment shifts.

Bubble Risk in AI? High. While AI is transformative, the market’s pricing of future growth may be overly optimistic. Investors should differentiate between companies with proven monetisation and those riding the hype.

What Should Investors Do?

Australia: The market is not in a full-blown bubble, but pockets of overvaluation exist—especially in tech. Diversification and a focus on fundamentals remain key.

United States: The US market shows stronger signs of speculative excess. Investors should be cautious with high-flying AI stocks and consider value and small-cap exposures.

AI: It’s real, it’s growing, and it’s monetising—but not all AI investments are created equal. Look for companies with clear revenue streams and sustainable business models.

Final Thoughts

Markets are cyclical, and bubbles are part of the investing landscape. The key is not to avoid investing altogether, but to invest wisely—with a clear understanding of valuations, earnings, and long-term potential.

If you’re unsure how to position your portfolio in this environment, consider speaking with one of our financial advisers who can help tailor your strategy to your goals and risk tolerance.

Jenni Anderson