DDI Controlled Vocabulary for Time Method


Describes the time dimension of the data collection.


Short Name:
Long Name:
Time Method
Version Notes:
The definitions listed under "Version Changes" were amended to make the terms clearer to users. The descriptive terms for TimeSeries, TimeSeries.Continuous, and TimeSeries.Discrete were edited to correct minor typographical errors.
Version Changes:
DEFINITIONS REPHRASED: Longitudinal, Longitudinal.CohortEventBased, Longitudinal.TrendRepeatedCrossSection, Longitudinal.Panel, Longitudinal.Panel.Continuous, Longitudinal.Panel.Interval, TimeSeries.Discrete, CrossSection, CrossSectionAdHocFollowUp
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DDI Alliance

Code List
Value of the Code Descriptive Term of the Code Definition of the Code
Longitudinal Longitudinal Data collected repeatedly over time to allow studying change in a population. At least some of the questions or modules are repeated over waves. Use the broad term when none of the subterms is suitable.
Longitudinal.CohortEventBased Longitudinal: Cohort/Event-based Data collected over time from the same cohort of respondents. The individuals in the cohort are connected in some way or have shared some significant experience within a given period. In some cases, the samples may differ between waves but are drawn from the same cohort. Examples: birth year, disease (clinical trials), common problem (intervention studies), education, employment, family formation, participation in an event.
Longitudinal.TrendRepeatedCrossSection Longitudinal: Trend/Repeated cross-section Data collected from different samples or different groups of people from the same population at several points in time, using at least partly the same set of questions/variables. Conclusions are drawn for the population. Examples: European Social Survey (ESS), national longitudinal crime surveys.
Longitudinal.Panel Longitudinal: Panel Data collected over time from, or about, the same sample of respondents. Differs from cohort/event-based data in that the selection of respondents is not based on their being connected in some way or having shared some significant experience.
Longitudinal.Panel.Continuous Longitudinal: Panel: Continuous Data collected from a panel of respondents on a regular basis.
Longitudinal.Panel.Interval Longitudinal: Panel: Interval Data collected from a panel of respondents only when information is needed.
TimeSeries Time series Data collected repeatedly over time to study change in observations. These are typically "objective" measurements of phenomena that can be observed externally, as opposed to attitudes/opinions or feelings. Examples may include economic/financial indicators, natural/meteorological phenomena, vital statistics, etc.
TimeSeries.Continuous Time series: Continuous Measurements are taken at every instant in time. Examples: lie detectors, electrocardiograms, etc.
TimeSeries.Discrete Time series: Discrete Measurements are taken at (usually regularly) spaced intervals. Examples: macroeconomics (weekly share prices, monthly profits, sales); meteorology (hourly temperature); measurements of individuals (blood pressure, weight, height); sociology (crime figures, employment figures), etc.
CrossSection Cross-section Data collected by observing subjects within the study period, without regard to changes over time. May include more than one collection event. Analysis of cross-sectional data often consists in comparing the differences and similarities among subjects.
CrossSectionAdHocFollowUp Cross-section ad-hoc follow-up Data collected at one point in time to complete information collected in a previous cross-sectional study; the decision to collect follow-up data was not included in the original study design.
Other Other Use if the time method is known, but not found in the list.


A brief textual description or classification of the type of the time methodology used. Supports the use of an external controlled vocabulary.

Module Name Element Name
datacollection TypeOfTimeMethod

The time method or time dimension of the data collection. The "method" attribute is included to permit the development of a controlled vocabulary for this element. For forward-compatibility, DDI 3 XHTML tags may be used in this element.

Element Number in DDI 2.1 Element/Attribute Name timeMeth@method

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