Frequently Asked Questions (FAQ)
What is AHTUS-X?
What is AHTUS?
What's in the future for AHTUS-X?
Does AHTUS-X add value to the data?
Where should a new user start?
How do I get access to AHTUS-X data?
What are microdata?
What are "weights"?
What does "universe" mean in the variable descriptions?
What is the difference between rectangular and hierarchical data?
What are time use variables?
Using the system
Can I delete previously created time use variables?
Is there a limit on the number of time use variables I can include in an extract?
How do I obtain data?
What is the format of the data?
How long does a data extract take?
How does "sample selection" work on the AHTUS-X web site?
What does "add to cart" mean?
Why can't I open the data file?
Is there a preferred statistical package for analyzing extracts created using the data extract system?
Can I analyze AHTUS-X data online without a statistical package?
Can I get the original AHTUS-X data?
Using AHTUS-X data
What are the major limitations of the data?
How do I cite AHTUS-X?
Using the variables page
Variables page menu
Variables page details
Using the data extract system
Your data cart
Why are some variables in my data cart preselected?
What is "Type"?
Extract request page
re> Extract definition: Data structure
Extract option: Describe your extract
General information about the project
What is AHTUS-X? [top]
AHTUS-X is a project dedicated to making it easy for researchers to use data from American Heritage Time Use Study. The AHTUS-X is a database of national time-diary samples collected over six decades, includes harmonized background, activity, location, mode of transport and who else was present variables. The dataset is administered by the Center for Time Use Research (CTUR) at University College London. CTUR is the responsible of creating documentation available and harmonizing data.
Time diary data allow researchers to look at how much time people spend doing different things. For certain purposes, it may be of interest to look at activities that people do at particular times of day (for example, paid work that occurs between 11 p.m. and 7 a.m.), in different locations (for example, paid work done at home) or during which the respondent had a child in their care. IPUMS-Time Use offers flexible tools for creating time use variables based on the different databases.
Codes are uniform across all of the data collection years and bring relevant documentation into a coherent form to facilitate analysis of the data. We provide descriptions of all of the variables we offer and, for categorical variables, codes and frequency counts for each year they exist in the data.
AHTUS-X is composed of microdata. Records may be at the person or activity level. All characteristics on each record are numerically coded. These respondents report all of the activities they engaged in over a 24 hour period. Each activity that is reported constitutes a separate record. Because the data consist of records that refer to individuals and the activities they engage in and not tables, researchers must use a statistical package to analyze the data. The data access system allows users to select only the years and variables they require.
What is AHTUS? [top]
The American Heritage Time Use Study (AHTUS), a database of national time-diary samples collected over six decades, includes harmonized background, activity, location, mode of transport and who else were present variables. The AHTUS is suitable for a wide range of investigative purposes.
The initial development of this project allowing release 1 in May 2006 was conducted under an agreement with Yale University (Program on Non-Market Accounts), and was sponsored by the Glaser Progress Foundation. Some amendments to this dataset made from December 2005 through December 2011 were funded by the Economic and Social Research Council. Since January 2012, further additions and upgrades to the AHTUS have been funded by a combination of grants provided by the Economic and Social Research Council and the National Institute of Child Health and Human Development.
What's in the future for AHTUS-X? [top]
Based on funding and data availability, AHTUS-X will release new data from the ATUS.
Does AHTUS-X add value to the data? [top]
The AHTUS-X data access system makes it easy for users to create the time use variables they want, thus making the data more accessible to a broader audience. The system aggregates time spent in user-specified combinations of activities and applies any requested filters behind the scenes and delivers this information to users in the form of a time use variable.
Users can select samples and variables they are interested instead of downloading the complete database.
Where should a new user start? [top]
The documentation is a natural starting place for new AHTUS-X users. We have a page dedicated to helping new users navigate our site.
The Variables page is the primary tool for exploring the contents of AHTUS-X. On the variables page, clicking on a variable name brings up its documentation. The documentation contains a description of the variable as well as the codes, labels, and frequencies for all categorical variables and availability of the variable across samples. This information can suggest the types of research possible with a given sample.
If you are already registered to use AHTUS-X, you can click on create an extract and use the data access system.
How do I get access to AHTUS-X data? [top]
Access to the AHTUS-X documentation is freely available without restriction; however, users must register in order to extract data from the website.
Note that each IPUMS project requires its own registration.
What are microdata? [top]
AHTUS-X microdata consist of individual records containing information collected on people, their households, and their activities. The unit of observation is the individual. The responses of each person to the different questions are recorded in separate variables.
Microdata stand in contrast to more familiar "summary" or "aggregate" data. Aggregate data are compiled statistics, such as a table showing the average amount of time each day that parents spend taking care of their children. There are no such tabular or summary statistics in the AHTUS data.
Microdata are inherently flexible. You do not need to depend on published statistics that compiled the data in a certain way, if at all. You can generate your own statistics from the data in any manner desired, including individual-level multivariate analyses.
What are "weights"? [top]
The weights perform two functions. First, the weights correct for imbalances between the population distribution and the diarist sample distribution. Where possible, the original sample weights are used, but in the earlier surveys where reliable weights were not available, weights that balance the distribution of the age and sex groups in relation to the Census or Current Population Survey distribution have been produced. In the case of the 1975-76 survey, new weights additionally account for attrition. Second, the weights correct for distribution of the days of the week. The American Time Use Survey (ATUS) collected half of diaries on weekdays and half on weekends. In all studies, diarists did not respond in equal numbers on each day of the week. As daily activity patterns do differ by the day - with the contrast between activities on Fridays, Saturdays, and Sundays being most distinct, it is important to rebalance the distribution of activities on the different days of the week.
RECWGHT is available for all surveys. This weight accounts for population/sample distribution by age group and sex, provides an even distribution of the days of the week (and corrects for the oversample of parents in the 1999-2001 element of the 1998-01 LOWQUAL diaries.
Two additional weights have been computed. The 1992-94 and the ATUS sampled all contiguous states, and the ATUS additionally included Hawaii and Alaska in the sample. The earlier surveys did not cover some of the smaller and more rural states nor did they include Hawaii and Alaska. As there is some possibility that these differences in the sample base may affect some results, we computed an additional weight, XTIMEWT. This cross-time weight is the same as the RECWGHT for the 1965-66, 1975-76 and 1985 surveys, but excluded the diarists from the additional states in 1992-94 and the ATUS (2003+). The ATUS original weights inflated the size of the sample to the size of the CPS population. We deflated the ATUS weights to reflect the actual sample size, but as the inflated weights are useful for some purposes, we produced an additional weight, INFLTWT, which retains the inflation factor for the ATUS (but still excluded those diaries excluded by RECWGHT by 0-weighting low quality diaries and diaries missing age, sex or day of the week the diary was completed). The inflation factor for the earlier surveys to reflect the CPS distribution for the relevant year is also available. As INFLTWT is based on RECWGHT, this weight retains those states found only in the most recent surveys.
What does "universe" mean in the variable descriptions? [top]
The universe is the population at risk of having a response for the variable in question. In most cases these are the households or persons to whom the question was asked. For example, only people who are employed are asked questions about their earnings on the job. Cases that are outside of the universe for a variable are labeled "NIU" in the codes and frequencies sections of the variable descriptions.
What is the difference between rectangular and hierarchical data? [top]
The AHTUS-X data access system delivers rectangular data by default. The rectangularized data file does not retain activities as separate records. Time use variables created in the system consisting of aggregated time spent in user-specified activities are delivered on the person record. With rectangularization, there is no separate activity in the data extract. No information is lost, and most researchers prefer this format.
AHTUS-X also delivers data files rectangularized at the activity level in which household and person information is repeated on each individual's activity records. To create a rectangular extract at the activity level, click on the 'Change Data Structure' button and select Rectangular -> Activity.
The rectangular format default can, however, be overridden to yield hierarchical data consisting of person records followed by the activity records. Users who request hierarchical data will need to select variables for inclusion in their extracts from the activity records. This is done on the same page in the extract builder as the selection of person level variables.
What are time use variables? [top]
Time use variables are user-defined combinations of activities and/or filters that limit attention to activity meeting certain conditions. Time use variables return the number of minutes respondents spend during the 24-hour reference period in activities matching the specified criteria. In AHTUS-X samples previous to 2003 respondents reported the activities they engaged in over a 24-hour period from 12 a.m. to 12 a.m. Starting in 2003, diaries starts at 4 a.m. and finish 4 a.m. In all samples respondents also reported where and when these activities took place. In some samples they also reported if they were doing a secondary activity, but this information is very limited in some samples.
You can create your own time use variables in the AHTUS-X data access system by selecting the activities of interest and restricting them to certain locations, times of day, secondary activities, and the presence of others. For example, if you were interested in studying shift work, you might create two time use variables by combining Work and Work Related activities with a time filter for two paid work shifts: first shift (7 a.m. to 3 p.m.) and second shift (3 p.m. to 11 p.m.). You could analyze the individual and occupational characteristics of individuals who work during the first shift with those who work during the second shift.
Using the system
Can I delete previously created time use variables? [top]
Our system does allow you to delete time use variables. Click on "Select data" in the top navigation bar; then select the option "Time Use" and click on "My Time Use Variables." From there you can see the time use variables you've created (click on the variable name to see more detailed information) and you can delete any time use variables you no longer want to use.
Is there a limit on the number of time use variables I can include in an extract? [top]
You may only include 50 time use variables in any given extract.
How do I obtain data? [top]
AHTUS-X data are delivered through our data access system. Users select the samples they are interested in, create and select time use variables, and select variables. The system then creates a custom-made extract containing only this information. To start, users can reference our instructions for opening an extract on your computer.
Data are generated on our server. The system sends out an email message to the user when the extract is completed. The user must download the extract and analyze it on their local machine. Access to the documentation is freely available without restriction; however, users must register in order to extract data from the website.
What is the format of the data? [top]
The data extract system produces fixed-column ASCII data. The data are entirely numeric. The extraction system rectangularizes the data by default, i.e. aggregates time spent in user-defined activities and puts time use variables on the person records.
In addition to the ASCII data file, the system creates a statistical package syntax file to accompany each extract. The syntax file is designed to read in the ASCII data while applying appropriate variable and value labels. SPSS, SAS, and Stata are supported. You must download the syntax file with the extract or you will be unable to read the data. The syntax file requires minor editing to identify the location of the data file on your local computer.
A codebook file is also created with each extract. It records the characteristics of your extract and should be downloaded for your records.
How long does a data extract take? [top]
The time needed to make an extract depends on the number and size of samples requested and the load on our server. Extracts can take from a few minutes to an hour or more. The system sends an email when the extract is completed, so there is no need to stay active on the AHTUS-X site while the extract is being made.
How does "sample selection" work on the AHTUS-X web site? [top]
When a user first enters the variable documentation system, all samples are selected by default. Every variable in the system will display on all relevant screens.
Users can filter the information displayed by selecting only the samples of interest to them. Only the variables available in one of the selected samples will appear in the variable lists. The integrated variable descriptions and codes pages will also be filtered to display only the text and columns corresponding to the selected samples. Sample selections can be altered at any time in your session. Selections do not persist beyond the current session.
When a user enters the extract system after selecting samples, those selections are carried into the data extract system.
What does "add to cart" mean? [top]
While browsing variables in the documentation system, you can place them into your data cart. Checkboxes and buttons labeled "Add to cart" are available in different contexts for this purpose. Any variables you identify in this way will be selected for you when you enter the data extract system. Once in the extract system, you can return to the variable list to make more selections.
Why can't I open the data file? [top]
The explanation is likely that you cannot open the data file directly with a statistical package. The file is a simple ASCII file, not a system file in the format of any statistical package. The extract system does, however, generate a syntax (set-up) file to read the ASCII file into your statistical package. You must download the syntax file along with the data file from our server, open the syntax file with your statistical package, and edit the path in the syntax file to point to the location of the data on your local computer. Now you are ready to read in the data.
Is there a preferred statistical package for analyzing extracts created using the data extract system? [top]
The data extract system supports SPSS, SAS and Stata. The system does not make data files in those formats, but generates syntax files with which to read in the ASCII data.
Can I analyze AHTUS-X data online without a statistical package? [top]
At this time, users are not able to analyze AHTUS-X data online.
Can I get the original AHTUS-X data? [top]
All original AHTUS-X data are available from the Center for Time Use Research.
Using AHTUS-X data
What are the major limitations of the data? [top]
The AHTUS-X data contain information for only one member of each household over one 24-hour period.
For more recent samples (2003 and after), with the exception of secondary child care (defined as having a child in one's care while engaged in another activity), secondary eldercare (defined as having an elder person in one's care while engaged in another activity), and secondary eating and drinking (collected as part of the Eating and Health module fielded from 2006 to 2008), information on secondary activities is not routinely collected.
Because the data are public-use, measures have been taken to assure confidentiality. Names and other identifying information are suppressed, and the geographic information recorded in the AHTUS-X data files is limited.
How do I cite AHTUS-X? [top]
Reports and publications using AHTUS-X data must be cited appropriately. The citation is:
If possible, citations should also include the URL for the AHTUS-X site: http://www.ahtusdata.org.
We ask that you notify us by email of any publications, research reports, presentations, or educational material making use of the data or documentation. Continued funding for the AHTUS-X depends on our ability to show our sponsor agencies that the data are being used for productive purposes.
Using the variables page
Variables page menu [top]
Use the "Variables" menu to browse or search variables:
Person: person variables by group
Activity: activity variables by group
Time Use: time use variables by group
Search: display only variables that contain specified text in particular fields
Use the buttons and links on the screen to:
Create a Time Use Variable: create user-defined aggregations of activities, locations, times, secondary activity, and co-presence of others
Select Samples: limit the display of variable information to selected samples
Rectangular/Hierarchical: chose a rectangular or hierarchical extract (more information)
Display Options: alter how the variable list is displayed or get help for this page
Variables page details [top]
The variables page allows you to browse variables while limiting and controlling how the information is displayed.
The "Variables" menu is for browsing the variables. You may also search variables by specifying search terms for specific fields of variable metadata. The system will return a list of variables that include any of the search terms you indicate.
When you "Create a Time Use Variable" you enter the time use variable creation process where you can load existing time use variables to use as templates for creating new variables or you can create new time use variables from scratch. You are required to name and label your time use variable before exiting the process or you lose the time use variable you have defined.
When you "Select Samples" you limit the variable list to display only variables that are available in at least one of those samples. But the effect of selecting samples extends into all the variable descriptions and codes pages you can access through the variable system. Only information relevant to your selected samples will be displayed in any context while you browse the variables. You can change your sample selections at any point.
The final choices are "Options" and "Help." The "Display Options" item brings up a screen that offers a number of choices regarding the display of the variable list. Each selection has a default choice.
View one group / View all groups
Switch between viewing one variable group at a time and viewing all variable groups on one screen. Unless you have a limited number of samples selected, your browser may be slow to display all groups. The default view is one group at a time.
Show availability detail / Show availability summary
Switch between displaying the full sample-specific availability matrix, and a view that only displays the total number of samples that contain each variable. Both views only display or sum the samples that the user has selected in "Select samples." The default view is the detailed availability information.
View available variables / View all variables
Switch between a view that only displays variables present in one of your selected samples, and a view that displays every variable, even if they are not available. The default view is to only display available variables.
Samples are displayed chronologically / Samples . . . reverse chronologically
Display the samples columns indicating variable availability in chronological order (oldest to newest) or reverse chronological order (newest to oldest). The default is reverse chronological (newest to oldest).
The Variable List
As you browse the variables, they are displayed in a list containing a number of columns. The variable name links to the variable description, which includes detailed comparability discussions, universes, and enumeration text. The variable codes -- and their associated labels -- can be accessed directly using the "codes" links. The "type" column indicates if it is a person or household variable. In some contexts, like the alphabetic view, the two types are pooled together.
In the area to the right of the "codes" column is a column for every sample that the user chose in "Select samples." By default, the most commonly requested samples from each year are selected. The country abbreviation and last two digits of the sample year identify each sample at the top of every column. Hover over the year with the mouse to see the full country name. If a variable is available in a given sample, an "x" is printed in that column.
Each variable has a box on the far left in the column labeled "Add to cart." Use these to identify variables you wish to include in a data extract.
Using the data extract system
Your data cart [top]
You must be logged in to use the data extract system. If you are not registered, you must apply for access.
At the top right corner of the variables page is a summary of your data cart. This box displays the number of variables and samples you have selected. Clicking the yellow circle next to a variable places it in your data cart. You can view your data cart at any time by clicking "View Cart." The "View Cart" link only becomes operative when you have selected a variable or sample.
You data cart lists the variables pre-selected by the extract system as well as any variables you selected while browsing the documentation. As with the variable selection page, you can remove variables from your extract in this step by clicking the checkbox next to the variable in the "Add to cart" column. If you chose a variable but subsequently altered your sample selections in such a way that the variable is no longer available, it is indicated by an "i" icon.
The data cart also includes record type, links to codes pages, and sample availability for the variables in your cart.
Buttons are provided to return to the variable list to make more selections or to alter your sample choices. If you return to the variable list, click on "View Cart" again to return to the data cart.
When you are satisfied with your data selections, click "Create Data Extract" to finalize your extract request.
Why are some variables in my data cart preselected? [top]
Certain variables appear in your data cart even if you did not select them, and they are not included in the constantly updated count of variables in your data cart.
Unless you are absolutely certain you will not need one of these variables, we recommend that you not remove them from your data cart.
What is "Type"? [top]
The "Type" column on the variables selection pages and in your data cart indicates the record type of the variable. The variables with a "P" are from the person record; the variables with an "A" are from the activity record. Activity records are not included in rectangular data files except as time use variables where the activity data serve as building blocks.
Extract request page [top]
When you click "Create data extract" in the Data Cart, you come to the Extract Request page. All of the actions on this page are optional. If you wish, you can simply hit the "Submit" button and create your data extract. You will be prompted to log in if have not done so already.
The page summarizes your data extract and provides a number of options for customizing it. A link at the top expands to show the samples you selected. If any samples have notes associated with them, a message will appear on the samples bar to encourage you to review that information. Click the appropriate links to go back to the variable browsing and sample selection pages to alter your choices. You return to the extract request page via the data cart, where you can review the availability matrix for selections and easily drop variables by unchecking them.
A separate link lets you choose the preferred data structure for your extract: rectangular (person or activity level) or hierarchical. Rectangular at the person level is the default format.
When you submit an extract, there will be a delay ranging from minutes to hours, depending on the size of the job. You do not need to wait on our site for the job to be completed. Our system will send you an email when your extract is ready.
The definitions of every extract will remain on our server indefinitely, but the data files are subject to deletion after three days. However, the screen where you download extracts has a feature that lets you revise old extracts. When you click on "revise," all your selections for that extract will be loaded into the system, after which you can edit or regenerate it. Note, however, that each successive data release can create difficulties for recreating old extracts, because codes might change.
re> Extract definition: Data structure [top]
You can choose the preferred file structure for your extract. Rectangular data at the person level only contain person records -- requested household information is attached to each household member. Rectangular data at the activity level includes household and person information repeated on each individual's activity records. Hierarchical data contains a distinct person record followed by a separate activity record for each respondent. The system defaults to rectangular person format, which is the overwhelming choice of researchers.
Extract option: Describe your extract [top]
You can describe your extract for future reference. Our system will display the description on the page where you download your data extract.