ABOUT THE DATASET:
In the Cumulative Data File, the ANES Project Staff has merged into a single data file cases and select variables from each of the American National Election Studies conducted from 1948 through 2004. Questions that have been asked in three or more Election Studies usually appear in the Cumulative Data File, but not always. The variables are coded in a comparable fashion across years.

October 31, 2005: A new version of the Cumulative Data File, including data from the 2004 ANES time series study, is now available.

Important: The ANES Cumulative Data File codebook is for use only with the ANES Cumulative Data File dataset with which it is paired. Conversely, the individual study codebooks are not appropriate for use with the ANES Cumulative Data File. There are many instances where the NES Cumulative Data File is different from the individual studies from which it is derived. Variation in records, frequencies, and other differences occur for a variety of reasons - for instance, additional information discovered since the release of an individual study, or the recoding across individual studies into a consistent set of codes. We strongly recommend that codebooks not be used with files other than those with which they were originally distributed.

STUDY OVERVIEW:
The ANES Project Staff has merged into a single data file cases and variables from each of the biennial American National Election Studies conducted since 1948. This file is called the ANES Cumulative Data File and is available from the Inter- university Consortium for Political and Social Research (ICPSR Study #8475).

Questions that have been asked in three or more Election Studies usually appear in the Cumulative Data File. The variables are coded in a comparable fashion across years. The version of the Cumulative Data File that is currently available pools data through the 2000 National Election Study to yield 44,715 cases. Note that the Cumulative Data File only includes data from the Time Series data collections (that is the Pre-/Post-Election Study in presidential election years and the Post-Election Study in midterm years). Data from other ANES studies, such as the 1984 Continuous Monitoring Study, the 1988 Super Tuesday Study, or the 1988-90-92 Senate Election Study, are not included in the Cumulative Data File.

Because each variable in the Cumulative Data File incorporates data for the same question from each of the ANES surveys, the file is particularly useful in service to three kinds of analysis: 1) analysis that focuses on over time change in citizens, in their individual characteristics, in the opinions they hold, and in their political behavior; 2) analysis that looks at subgroups of citizens that are represented by few cases in a single, cross-section sample, but by many more cases when several samples are combined; and 3) analysis that is concerned with replicating results over several elections. For these types of analyses, the chief advantage of relying on the Cumulative Data File, as opposed to combining, on one's own data from several National Election Studies, is that in constructing the Cumulative Data File, the ANES Project Staff have already gone through the trouble of recoding variables so that the same question has the same variable number and the same coding scheme for each of the Election Studies. A great deal of effort has gone into checking and verifying these recodes.

Those who use the Cumulative Data File should keep two things in mind: 1) the wording of questions occasionally changes over time to reflect changes in the political context in which the question is being asked. The NES Project Staff have done their best to document in the codebook any over time differences in question wording that have occurred; 2) even when a question is worded identically in successive surveys, analysts may still wish to examine the placement of the question in each questionnaire to ensure that changes in its placement are not contaminating one's results.

SAMPLES FOR ELECTION STUDIES IN THE CUMULATIVE FILE:
Over the years, the most common NES study design has been a cross-section, equal probability, sample. These designs are typically "self-weighting" -- i.e., the respondents do not need to be weighted to compensate for unequal probabilities of selection in order to restore the "representativeness" of the sample. On several occasions, however, ANES has departed from this standard design. In some years, ANES "oversampled" certain groups (African-Americans in 1964, for example). In other years, the Election Study combined a panel reinterview with a cross- section design (as in 1974, for example). It is important to understand that the Cumulative File is a file of pooled cross- section studies: any respondent for a particular study who is strictly "panel" or "supplement" has been deleted from the Cumulative File. For example, the sequence of studies 1972, 1974, and 1976, constitutes a panel, with cross-section respondents in 1972 and 1974 being reinterviewed in succeeding years. If a 1972 respondent moved out of the SRC sampling area, but was nevertheless reinterviewed, that respondent became a "panel only" respondent, and the representativeness of the 1974 cross-section was maintained by selecting a new respondent from the residents at the sample address from which the "panel only" respondent had moved. Such 1974 "panel only" respondents are not included among the 1974 respondents that appear in the Cumulative Data File.

Because not all of the cross-section samples included in the Cumulative Data File are equal probability and thus self- weighting, all pooled cross-section descriptive analyses should be run using Variable 9, the weight variable. For most years, the value of that variable for all respondents is simply "1.0"

The table below lists the cross-section sample sizes, weighted and unweighted, for each Election Study included in the Cumulative Data File.

*     note: the 1970 figures exclude 73 non-eligible Rs in the original dataset's cross-section N. The Cumulative File excludes all non-eligible respondents from its cross-section. For descriptions of type 0, type 1, and type 2 variables in 1970, see weight vars V9-11.

**     note: the weighted cross-section Ns are represented in the Guide to Public Opinion and Electoral Behavior, which was produced using data from the Cumulative File. To reproduce the data appearing in the Sourcebook, it is necessary to use appropriate weights (see V9-11).

***     note: 20 cases have been deleted from the 1990 Study data due to belated discovery of interview fabrication and ineligible Rs.

****    note: In 1994, 1996 and 2000 there are multiple weights which can be used with the data; see Study documentation.