Mega IPOs: looking beyond the headlines

As with many market developments, the answer is nuanced. Alongside the opportunities and risks these companies present, much of the current debate—both in markets and media - has centred on how they may be included in major indices.

This matters most for passive investors, where index construction directly shapes portfolio exposure. However, it also has broader relevance. The way new companies enter indices can influence market dynamics more widely - affecting valuations, investor behaviour, and the pace at which new areas of the economy are reflected across both active and passive portfolios.

Against this backdrop, it is worth looking beyond the headline valuations to consider how mega IPOs may affect portfolios over time - including where risks and opportunities may arise, and what this could mean for investors taking a long‑term view.

Why mega IPOs are in focus

While new listings are a regular feature of markets, the scale and profile of some of these forthcoming IPOs – such as SpaceX, OpenAI and Anthropic – make them stand out. These companies are often already large, globally recognised and positioned in fast‑growing areas of the economy.

As a result, they can enter public markets with significant valuations and strong investor interest from the outset, even as they continue to develop their commercial models. This transition from private to public ownership can bring both opportunity and uncertainty, particularly as markets assess their longer‑term earnings potential.

Where risks and opportunities may lie

Earlier access to new growth areas
One of the clearest opportunities is earlier access to emerging sectors. These upcoming mega IPOs can provide public market investors with exposure to areas such as artificial intelligence, next‑generation technology and aerospace that have, until now, largely sat in private markets.

This can broaden the opportunity set for investors. However, it also means exposure to companies that are still evolving, where future growth and profitability may be less certain than for more established businesses.

Liquidity and timing dynamics
One of the more subtle considerations is how supply and demand interact around a new listing.

At the point of IPO, only a relatively small proportion of shares is typically available to trade, while a much larger portion remains held by founders, early investors and employees. 
At the same time, strong investor interest - particularly around high‑profile IPOs - can lead to significant demand.

This imbalance can influence price behaviour in the early stages, where market movements can be driven as much by positioning and sentiment as by fundamentals. Over time, as more shares become available and trading settles, price discovery tends to become more balanced.

The role of lock‑ups and insider selling
Most IPOs are subject to lock‑up periods, where early investors, founders and employees are restricted from selling shares for a period after listing. These typically expire several months after listing.

When these restrictions expire, additional shares may come to market, increasing liquidity. While this is a normal part of the listing process, it can lead to phases where supply increases and prices adjust as a result.

For investors, this creates a shifting dynamic:

• Early on, prices may be influenced by limited supply and strong demand;
• Later, the release of additional shares can introduce more normal market liquidity, but also periods of adjustment as supply increases.

For long‑term investors, this highlights that the path after listing is rarely linear, even for high‑quality companies.

Volatility and expectations

High‑profile IPOs often attract considerable attention, which can raise expectations.

In practice, newly listed companies often experience higher volatility, particularly as markets assess their valuation, growth trajectory and ability to deliver on expectations.
Over time, performance tends to become more closely linked to fundamental progress rather than initial sentiment.

How index rules influence portfolio exposure

As investors increasingly adopt a mix of active and passive approaches, exposure to new companies can vary depending on how those strategies are implemented—particularly where passive allocations track specific indices.

Index providers take different approaches to including new companies. Broad, rules‑based indices such as MSCI and FTSE may include these mega IPOs relatively quickly once size and free‑float thresholds are met. Others, such as the S&P 500, require a track record of profitability, while more growth‑oriented benchmarks, including parts of the NASDAQ index family, may reflect them earlier due to their sector focus.

As a result, exposure to new companies—and the sectors they represent—can emerge at different points depending on the index. However, the immediate impact is often smaller than headline valuations suggest, as newly listed companies typically float only a portion of their shares, resulting in modest initial index weights.

Over time, as more shares become available and index weights adjust, exposure can build. While this increases the holdings in a portfolio, it does not always lead to broader diversification. In some cases, exposure may become more concentrated in certain sectors – e.g. holdings in growth‑oriented sectors may rise, meaning portfolios can become more tilted towards certain parts of the market rather than more diversified overall.

What could this mean for portfolios?

In the near term, the impact of mega IPOs on diversified portfolios is typically limited, with initial allocations relatively small and performance driven by a wide range of factors.
Over time, their influence may grow as these companies become more widely held and more fully reflected in public markets.

More broadly, mega IPOs are part of a longer‑term trend: the ongoing evolution of markets as new companies and sectors emerge. For investors, what matters is not any individual listing, but how portfolios remain positioned to capture opportunities while managing risk over time.

Final thoughts

Mega IPOs are likely to play a growing role in global equity markets in the years ahead, reflecting innovation and growth in new areas of the economy.

While much of the current attention has focused on index inclusion and short‑term market dynamics, the longer‑term implications are more balanced. These developments bring both opportunities for growth and periods of adjustment as companies transition into public markets.

For investors, the key remains unchanged: maintaining a disciplined, long‑term approach, ensuring portfolios remain well diversified, and avoiding the temptation to react to individual market events.
 

Disclaimer:

Please note that past performance is not an indicative of future performance, and the value of an investment with St. James’s Place will be directly linked to the performance of the funds selected and may fall as well as rise. You may get back less than the amount invested.

The value of an investment in equities and shares may go up and down. You may get back less than the amount invested. This is different to the capital security typically associated with bank deposits held in cash.

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