Some companies move the market every time they publish an RNS. Others can release results, contract updates or strategic announcements and barely generate a ripple in their share price. This difference raises an interesting question for investors: which companies consistently generate the highest levels of volatility when they communicate with the market? The concept of an RNS Volatility Index provides a framework for measuring the average share-price movement associated with a company's announcements. Using historical share-price behaviour from Google Finance and disclosure activity across the London Stock Exchange, investors can assess which issuers routinely surprise the market and which maintain highly predictable communication records.

What Is the RNS Volatility Index?

The RNS Volatility Index measures the average share-price movement generated following corporate announcements. A simplified methodology would assess:

  • Same-day share-price movement.
  • Intraday trading range.
  • One-week follow-through.
  • Frequency of large price moves.
  • Relative movement versus sector peers.

Companies consistently producing large reactions would score highly, while businesses generating modest and predictable reactions would rank lower. Importantly, a high volatility score is not inherently positive or negative. It simply indicates that announcements regularly contain material new information that changes investor expectations.

Why Some Companies Generate More Volatility

Several factors determine how strongly investors react to company announcements.

Information Asymmetry

Companies with limited analyst coverage often experience larger post-announcement moves because investors possess less information before the news is released.

This is particularly evident among:

  • AIM companies.
  • Small-cap technology firms.
  • Exploration companies.
  • Development-stage biotechnology businesses.

For these issuers, a single announcement can significantly alter market perceptions.

Business Model Complexity

Businesses operating in emerging industries frequently generate stronger reactions because future earnings are more difficult to predict.

Examples include:

  • Artificial intelligence.
  • Biotechnology.
  • Defence technology.
  • Early-stage energy transition projects.

Where uncertainty is highest, each new disclosure carries greater valuation implications. AI-related disclosures and technology-driven business updates have become increasingly prominent across UK-listed companies in recent years.

Guidance Frequency

Companies providing regular and detailed updates often generate lower average volatility because investors receive information continuously.

By contrast, businesses communicating infrequently can experience larger share-price adjustments when significant updates finally arrive.

The Highest-Volatility Sectors

Biotechnology and Life Sciences

Volatility Score: Very High

Biotechnology companies would likely dominate any RNS Volatility Index.

Typical volatility catalysts include:

  • Clinical trial results.
  • Regulatory approvals.
  • Licensing announcements.
  • Research milestones.

A single announcement can transform future revenue assumptions, creating substantial one-day gains or losses.

Mining and Exploration

Volatility Score: Very High

Resource companies regularly generate dramatic reactions through:

  • Drilling results.
  • Resource estimates.
  • Discovery updates.
  • Permit approvals.

Because underlying asset values are often uncertain, the market reacts aggressively to new geological information.

Technology

Volatility Score: High

Technology firms frequently produce significant volatility through:

  • AI announcements.
  • Product launches.
  • Strategic partnerships.
  • Customer wins.

The strongest reactions typically occur when new information affects future growth expectations.

Defence

Volatility Score: High

Defence companies have become increasingly market-sensitive as investor attention has grown around procurement spending, autonomous systems and national security technologies. Major contract awards often trigger sizeable share-price movements.

The Lowest-Volatility Sectors

Utilities

Volatility Score: Low

Regulated business models and stable cash flows generally result in smaller market reactions.

Investors often have strong visibility over future performance, reducing the informational impact of individual announcements.

Consumer Staples

Volatility Score: Low to Moderate

Established consumer businesses typically experience relatively predictable trading patterns and earnings streams.

As a result, announcements rarely trigger extreme valuation adjustments.

Large Financial Institutions

Volatility Score: Moderate

Banks and insurers publish extensive data throughout the year, reducing the surprise element surrounding most announcements.

Significant movements generally occur only when earnings diverge materially from expectations.

Characteristics of High-Volatility Issuers

Analysis of historical market behaviour suggests that companies generating the highest announcement volatility often display the following traits:

Small Market Capitalisation

Smaller companies are typically more sensitive to news because:

  • Liquidity is lower.
  • Analyst coverage is limited.
  • Information gaps are larger.

A transformational contract or operational update can therefore produce outsized effects.

Concentrated Revenue Sources

Companies dependent on:

  • A small number of customers.
  • A handful of projects.
  • Specific regulatory approvals.

often generate greater volatility because each announcement has a larger potential impact on future earnings.

Emerging Growth Themes

Businesses exposed to major market themes tend to generate stronger reactions.

Current examples include:

  • Artificial intelligence.
  • Defence innovation.
  • Energy security.
  • Cybersecurity.

Investor attention amplifies the impact of related announcements

What Generates the Biggest RNS Moves?

Historical analysis suggests that the largest volatility spikes typically follow:

  1. Profit warnings.
  2. Takeover approaches.
  3. Clinical trial outcomes.
  4. Major contract awards.
  5. Earnings upgrades.
  6. Strategic acquisitions.
  7. Emergency fundraisings.
  8. Regulatory approvals.
  9. Significant director buying clusters.
  10. Resource discoveries.

These announcement categories directly affect expectations regarding future value creation.

A Hypothetical RNS Volatility League Table

If issuers were grouped by average announcement impact, a typical ranking might resemble:

Very High Volatility

--------------------

Biotechnology

Junior Mining

Exploration Energy

Early-Stage Technology

 

High Volatility

---------------

Defence Technology

Software

Industrial Growth Companies

Specialist Engineering

 

Moderate Volatility

-------------------

Financial Services

Asset Managers

Property Companies

Consumer Cyclicals

 

Low Volatility

--------------

Utilities

Consumer Staples

Infrastructure Assets

Large Regulated Businesses

The ranking reflects announcement sensitivity rather than investment quality.

High Volatility: Opportunity or Risk?

The answer depends on investor objectives.

Opportunities

High-volatility issuers can provide:

  • Significant upside potential.
  • Faster re-ratings.
  • More event-driven opportunities.
  • Greater inefficiencies.

These characteristics appeal to active investors.

Risks

The same companies also face:

  • Larger drawdowns.
  • Greater earnings uncertainty.
  • Wider valuation swings.
  • Increased financing risk.

High volatility amplifies both gains and losses.

The Link Between Volatility and Disclosure Quality

Interestingly, high volatility does not necessarily indicate poor communication.

In many cases, the opposite is true.

Companies releasing material operational data, measurable milestones and meaningful updates often generate stronger reactions precisely because investors trust the information being provided.

The distinction lies between:

  • Volatility caused by new information.
  • Volatility caused by uncertainty.

The former is often healthy. The latter is typically more problematic.

What Investors Should Watch

When assessing a company's RNS Volatility Index profile, investors should consider:

  • Frequency of major price movements.
  • Quality of disclosures.
  • Historical guidance accuracy.
  • Sector dynamics.
  • Market capitalisation.
  • Analyst coverage levels.

A consistently high volatility score may indicate a stock worth monitoring closely around announcement dates.

Conclusion

The RNS Volatility Index offers a useful lens through which to view corporate disclosures and investor behaviour. Analysis of historical share-price movements and London market disclosure trends suggests that biotechnology, mining, technology and defence companies generate the largest average reactions because each announcement has the potential to reshape expectations for future earnings and growth. Meanwhile, utilities, consumer staples and mature financial institutions generally produce lower announcement-driven volatility due to more predictable business models and greater earnings visibility. Understanding which companies consistently move the market can provide a valuable edge. After all, in a market increasingly driven by information, some companies don't just release news, they create it.