What is Longitudinal Research?

Understanding Longitudinal Research

Longitudinal research is one of the most significant research projects conducted in market research. These studies empower companies with valuable insights into the shifts in consumer behavior, market dynamics, and the effectiveness of strategies by adeptly identifying trends, patterns, and changes over time. This long-term perspective fosters a comprehensive understanding of the complex consumer and competitive landscape. By incorporating longitudinal research into their market research mix, businesses can make informed, adaptive decisions that lead to sustained success.

Importance and Uses of Longitudinal Research

Longitudinal research studies are market research studies that collect data on a topic over an extended period by leveraging different waves of research using the same questions, allowing for comparability wave-to-wave.

This ability to examine and track changes, developments, and patterns over time makes longitudinal research so important. Some of its uses include:

Understanding Changes Over Time

Longitudinal research is crucial for tracking changes in variables, behaviors, or trends over an extended period, enabling researchers to identify patterns and developmental trajectories. This can include brand awareness, brand rating, loyalty, purchase intent, brand rating, competitive advantage, marketing impact, and more.

Causality Assessment

Longitudinal research helps companies establish cause-and-effect relationships by observing the influence of one variable on another over time, contributing to a more in-depth understanding of causal mechanisms.

Marketing Effectiveness

Organizations can utilize longitudinal research to measure the effectiveness of their marketing efforts, allowing them to make adjustments to better connect with their target audience.

Distinction Between Longitudinal and Cross-Sectional Research

The key distinction between longitudinal and cross-sectional research is the timeframe in which the data is collected. With cross-sectional research, data is collected at a single point in time with the aim of providing a snapshot of that specific moment. Longitudinal research, through repeated observation of the same individuals or groups over time, collects data with the objective of identifying trends or patterns in behavior and attitudes. 

Another key distinction between the two types of studies is the needed resources (time, money, people, etc.). Since cross-sectional research consists of one-time snapshots, it is generally more flexible and quicker to conduct while also requiring fewer resources. The long-term nature of longitudinal research is often more resource-intensive and time-consuming.

The Process of Conducting Longitudinal Research

When a business wants to conduct longitudinal research, there are some key steps in the process they need to be aware of to ensure they get the insights and value they are looking for.

Building a Sample Plan

The foundation of any longitudinal research study lies in crafting an effective market research sample plan that ensures consistency and reliability throughout the life of the study. The criteria around sample size, target audience, demographics, psychographics, panels, and other factors must be meticulously defined. Understanding what targeting is feasible and what isn’t also needs to be considered.

Data Collection Methods in Longitudinal Research

The richness of insights gleaned from longitudinal research is intricately tied to the choice of data collection methods. While a longitudinal survey is the most common approach, other methods like digital tracking and specialized market research techniques can also be employed to gather data over time.

Time Span and Follow-Up Periods in Longitudinal Research

Finally, determining the optimal timespan and follow-up periods for longitudinal research is pivotal. A balance of capturing meaningful data with practical constraints needs to be evaluated. Essentially, organizations need to determine how frequently and for how long they want to conduct their research.

Advantages of Longitudinal Research

In-Depth Understanding of Consumer Behavior

Longitudinal research offers companies the advantage of gaining an in-depth understanding of consumer behavior and how it changes over time. By tracking changes in preferences, purchasing patterns, and brand loyalty, they can uncover unique insights beyond just a spot-in-time snapshot, allowing for more informed decision-making. 

Causality Assessment for Marketing Strategies

Another advantage lies in the ability of businesses to assess causality in the effectiveness of their marketing strategies via longitudinal research. It enables them to identify the impact of specific marketing initiatives over time, distinguishing between short-term fluctuations and sustained effects. This causality assessment is invaluable for refining and optimizing marketing approaches for sustained success.

Adapting Strategies for Evolving Market Dynamics

Longitudinal research equips businesses with the capability to adapt their marketing and overall strategies to evolving market dynamics. Companies can make real-time adjustments by continuously monitoring variables such as consumer preferences, competitive landscapes, and economic influences, ensuring that their market strategies remain relevant and responsive to changing conditions.

Comprehensive Brand and Market Insights

By tracking different variables over time, longitudinal research provides businesses with comprehensive brand and market insights that can often be applied to the general population. This includes tracking brand perception, market trends, and the overall effectiveness of promotional activities. This holistic understanding enables companies to refine their brand positioning and marketing efforts for sustained success.

Challenges of Longitudinal Research

Feasibility / Sample Attrition

One significant challenge with longitudinal research is maintaining sample feasibility over the life of the study. As studies progress through multiple waves of research, finding the necessary number of respondents becomes increasingly challenging. This is due to sample attrition — where respondents naturally leave panels over time — and restrictions on respondent reuse. These factors, among others, can not only impact your ability to achieve your desired sample size but also introduce bias and compromise the comparability of results across different waves of research.

Resource Intensity and Time Commitment

Another challenge in longitudinal research is the resource intensity and time commitment needed for this type of market research. They often require substantial investments in terms of time, personnel, and financial resources. The need for repeated measurements and prolonged study periods can pose practical challenges for businesses with limited resources.

External Influences and Market Volatility

Longitudinal research can be susceptible to external influences and market volatility. Economic changes, unexpected events, or shifts in consumer behavior influenced by external factors can complicate the interpretation of trends and patterns. Controlling these external variables becomes challenging, requiring careful consideration in research design.

Data Analysis Complexity

Analyzing the vast amount of longitudinal data collected over an extended period poses a challenge. The complexity of longitudinal data analysis increases when different waves of research are examined to identify meaningful patterns and trends. Advanced statistical models and sophisticated analytical methods are often required to interpret the data properly, and understanding the dynamic interplay of variables demands careful consideration by a company.

Learn more about the pros and cons of longitudinal studies.

EMI – Longitudinal Research Experts

Longitudinal research is one of the most essential studies fielded in consumer market research. It’s used by large brands, consumer goods companies, and others to track consumer sentiment around their products or services and to measure advertising and other functions of the marketing mix.

Here at EMI, our unequaled knowledge of the sample panel landscape combined with our strategic sample blending approach has made us experts in building customized sample plans for longitudinal research that deliver high-quality, reliable results. Our custom strategic sample blends are crafted intentionally and controlled, where panels are selected to complement each other while reducing the overall sample bias and any potential behavioral or attitudinal impacts a panel can have.

Download our whitepaper Strategic Sample Blending: The Premier Sample Methodology for Tracking Studies to learn about sampling challenges and how strategic blending can solve them.

Strategic Sample Blending

EMI is unique in that we don’t just blend sample for the sake of blending. We do it with quality and consistency in mind, understanding that not all techniques for combining multiple sample panel providers are created equal. In other methods of combining sample, like stacking, no care is given to panel makeup, respondents’ attitudes and behaviors, or panel bias, and this is often done in a final effort to reach feasibility goals. We know that customizing a strategic blend based on clients’ unique needs will ensure the best results possible. So, what does strategic sample blending entail? 

Strategic sample blending takes sample blending a step further. Not only do you use three or more sample providers, but the selection and blending of the selected providers is intentional and controlled. Sample sources are chosen to complement one another, providing a balanced representation that maximizes data quality and research reliability. This ensures the accuracy of your data and that it genuinely represents your target audience’s demographics, behavior, and attitudes.

Additionally, by strategically selecting your providers and managing their allocation, you can increase your overall feasibility for the life of your tracker, avoiding the dreaded “top-up” situation that can skew your data. By strategically blending sample, you can ensure the consistency and reliability of your longitudinal research and the data it provides, allowing your organization to make the best business decisions possible.

So, how do we do this? 

We start with a typical blend formula and then customize it based on various criteria so that the strategic blend ensures you will meet the goals of your study. After considering all the factors, we develop your strategic blend through a methodical process. We map potential panel partners across essential criteria to identify those that hit the optimal balance — delivering both the consistency and feasibility needed throughout your study’s lifecycle. We also balance the provider’s attitudes and behaviors to eliminate bias. 

Discover more about strategic sample blending, the best-in-class approach to sampling for online quantitative studies, here.

IntelliBlend®

IntelliBlend® is EMI’s premier strategic sample blending methodology, perfectly suited to longitudinal research. It involves blending sample sources in an intentional and controlled approach to deliver the most representative and accurate demographic, behavioral, and attitudinal data. This approach includes double opt-in research panels but may also include non-traditional sources such as social media, which is utilized in a limited and controlled manner.

IntelliBlend can vary from project to project based on the research needs and the client. The unique blend is developed by leveraging proprietary research-on-research data and over 20 years of sample experience. For ongoing work, the custom sample plan is replicated from wave to wave utilizing EMI’s sample management platform, SWIFT, which enforces sample source quotas, ensuring data consistency.

Learn more about IntelliBlend here.

Making Adjustments to Longitudinal Research

You may think building a strategic blend is the end, but it isn’t.

Through our research-on-research process, we know that panels are not only different from one another but also change over time. Since longitudinal research studies are critical for organizations to make crucial decisions, consistency in the data is necessary. Adjustments must be made to ensure data consistency in your longitudinal research, including the sample providers you use and their allocations.

Numerous factors may cause you to adjust the sample allocation of your providers or your decision to work with specific sample providers, including:

• Changes in base size
• Changes in length of interview (LOI)
• Changes to the incidence rate (IR)
• Changes to the sample quotas
• Feasibility of one or more of your sample providers
• Poor or declining data quality
• Mergers/Acquisitions in the sample industry

Similarly, there is a variety of criteria that we can control when creating your blend, including:

• Attitudes and Behaviors by panel
• Client KPIs
• Feasibility
• Targeting Criteria
• Fielding Time & Fielding Criteria
• And much more

When you are looking to adjust your longitudinal research, we have five key recommendations you should follow:

• Monitor all KPIs by sample provider over time.
• Have at least one or more sample provider that provides a small amount of completes per wave but can increase their allotment of completes if necessary.
• Make slight adjustments to sample partner blends to start. Immediate significant changes may have adverse impacts on KPIs.
• Maintain full transparency between the research, client, and sample teams and ensure everyone understands the advantages and disadvantages of adjusting the blend.
• Work with a sample expert to help identify like panels to ensure minimal impact on KPIs.

Transitioning Longitudinal Research to EMI

EMI’s strategic sample blending methodology ensures we can help transition any longitudinal research, no matter the scenario you currently face. We build a controlled and intentional strategic blend to help you meet your study’s goals while also reducing bias and ensuring consistency over time.