Identifying opinion leaders and elites: a longitudinal design.

ABSTRACT

The term longitudinal design refers to a flexible research approach that can be applied to a wide range of topics involving change over time. Longitudinal refers to both the data collected and the methods of analysis used, and project designs can combine several data-gathering and analysis methods within a longitudinal framework. Longitudinal research demonstrates several features that permit the observation of process and change and facilitate identification and evaluation of the underlying factors. Several library and information science studies demonstrate the application of a longitudinal approach to both prospective and retrospective research questions. This article draws primarily on a longitudinal study of leaders who emerged in the archival profession during the 1980s when archivists developed the first set of descriptive standards (MARC AMC) in response to trends in the automation of library cataloging. The study identified a core group of leaders whose influence drove the archival profession to move in a specific direction. The identification of opinion leaders and elites, and the factors that led to their status, has significant implications for understanding patterns of decision making and communication within organizations.

INTRODUCTION

The terms longitudinal design and longitudinal analysis apply to a wide range of research studies conducted within many social science disciplines. The concept of longitudinal research relates to both the nature of the data and the methods of analysis. Because researchers can use a longitudinal approach in combination with other methods, as well as by itself, the longitudinal nature of a study is not always obvious. Research that focuses on process, adaptation, or change is often longitudinal, whether or not that element of the design is clearly articulated. The common denominator in all cases is time; in longitudinal research a span of time provides the crucial insight into the questions being studied.

This article examines longitudinal design and analysis as a research method, reviewing ways in which researchers have defined and applied this approach. Examples of longitudinal studies in library and information science (LIS), broadly defined, provide context for understanding why researchers choose this method and its strengths and weaknesses. These examples illustrate the kind of problems for which a longitudinal design is appropriate.

The article also focuses on a longitudinal research study by the author that analyzed changes in the archival profession during the 1980s, a period that experienced rapid change within archives and the adoption of the first set of descriptive standards, that is, the US MARC format for Archival and Manuscript Control (MARC AMC) (Davis, 2003b). The study sought to identify the opinion leaders within the profession and to understand how they were able to persuade and mobilize archivists to undertake what was viewed as a radical change in outlook and practice.

DEFINITIONS AND CHARACTERISTICS

The terms longitudinal design and longitudinal analysis have been used to describe a wide range of research using many different approaches. In fact, one of the strengths of longitudinal design is that it can serve as a framework for research that combines a longitudinal approach with other methods of data collection and analysis. Menard says that "longitudinal research must be defined in terms of both the data and the methods of analysis used in the research" (2002, p. 2). Following that line of reasoning, the term describes not one but a variety of methods that demonstrate the following features:

* Research covers a span of time in order to document process or identify change

* The direction of the research can be prospective or retrospective

* Data can be qualitative or quantitative

* Data should encompass multiple units of analysis

* Data collection should occur more than once

Researchers have elaborated on these points in their discussion of the method and its potential application to different kinds of research questions. Kimberly says: "Longitudinal organizational research consists of those techniques, methodologies and activities which permit the observation, description and/or classification of organizational phenomena in such a way that processes can be identified and empirically documented" (1976, p. 329). He goes on to point out that the researcher defines the length of time for the project, as well as the research objectives, number of data collection periods, duration of time between collection periods, method of analysis, and unit of analysis. Venkatesh and Vitalari, who applied longitudinal analysis to information systems research, stated that "longitudinal research examines the behavior of processes and change in critical variables over time" (1991, p. 2). They also point out the benefits of using multiple methods to collect data in a variety of forms. According to Janson, "a 'longitudinal study' can be any diachronous study or a study of a process of change" (1981, p. 20). Diachronous refers to looking at changes over time, in contrast with synchronous, which is the analysis of factors existing or arising at a single point in time. This time span aspect is the primary factor that distinguishes longitudinal research from other approaches.

The basic definition does not specify whether the chronological direction is forward or backward. The majority of longitudinal research is prospective, however, because it is easier to plan to collect specific information in the future than it is to derive it after the fact. As King stated:

 
   The main difference between prospective and retrospective designs 
   is the length of the recall period. In prospective designs the 
   recall is generally closer to and captured as the phenomenon 
   unfolds, while retrospective designs require the participants to 
   recall events that have happened in the past. Intervening 
   experiences and events can interfere with the accuracy of data 
   in recalled events. (2001, p. 10) 

However, the risks are lessened through careful and probing questions from the researcher. In addition, not all retrospective data result from interviews; one can also tabulate data from secondary sources.

The definitions also do not specify whether the data collected and analyzed are quantitative or qualitative. Longitudinal research is frequently quantitative in nature, although it can combine both qualitative and quantitative approaches. Ruspini (1999) suggests that research based on longitudinal data can build bridges between qualitative and quantitative research traditions. The terms qualitative and quantitative can apply to both the data and the analytic techniques.

Whatever data is collected should encompass a number of units of analysis, and the data should be collected on those units at more than one point in the study to allow comparison over time. Janson (1981) limits longitudinal research to studies that collect data on the same individuals or units at multiple points and that also use data on several of those units. He suggests that longitudinal analysis is sometimes treated as synonymous with cohort analysis, where the term cohort "has a very wide meaning of any subpopulation of individuals (or other units) with a common characteristic" (p. 21). Researchers also contrast longitudinal research with cross-sectional research where measurement occurs only once for each subject or variable.

Within those definitions, research design and data collection can include a range of methods, including panel and cross-sectional designs, interviews, and survey research. Longitudinal studies have been undertaken within the fields of anthropology, community studies, education, psychology, health, and criminology and can focus on transitions, changes, and adaptations, as well as the impact of events and circumstances (Holland & Thomson, 2004). Longitudinal research has many advantages and is particularly appropriate for studying social change and the diffusion of innovations. Menard suggests that "For many, longitudinal research is touted as a panacea for establishing temporal order, measuring change, and making stronger causal interpretations" (2002, p. 1).

Researchers frequently examine…