What Kind of Data or Statistics Do You Need?
Before you can start looking for data or statistics, you need to know what you need.
- Do you need statistics, or do you need data? A statistic is a single number that has been computed to summarize some larger quantity of data. "In 2011, 45 percent of Americans favored legalizing same-sex marriages" is a statistic. (That statistic came from a survey by the Pew Research Center.) Sometimes, a statistic is all you need. Other times, you'll need data that you can analyze yourself to compute your own statistics. In this example, data would be a file containing the answers given by each of the 1504 people who responded to the Pew Research Center's survey.
- What geographic area(s) are you interested in? A single country? Comparing multiple countries? States, counties, provinces, districts, or other small areas?
- Who is likely to collect and publish the information that you need? There are many different kinds of statistics and data, collected by many different kinds of organizations.
- Much data, including demographic (population-related), economic and climate data, is usually collected by governments and intergovernmental organizations (e.g., the World Health Organization). Examples of this type of data include unemployment rates, malaria infection rates, and weather records.
- Public opinion data is usually collected and published by specialized polling organizations.
- Election returns are also published in specialized databases.
- Some data can only be collected by small-scale surveys or experiments. For example, do students in classes that use an experimental new curriculum fare better or worse than students in other classes?
Where Can You Find the Data or Statistics You Need?
Once you know whether you need statistics or data, and once you've decided what kind of data you need and for what geographic areas, you're ready to start your data search. Follow the steps below to find the statistics or data you need.
1) Do you need statistics?
- YES, I need statistics: Can you find an article (scholarly or newspaper) containing the statistics? If it's a scholarly article, you may be able to cite the article itself as the source of the statistics. Otherwise, you can use the references in the article to find the original source of the statistics. If you can’t find an article with the statistics you need, go to step 2.
- NO, I need data: Go to step 2.
2) Do you need numbers that governments or intergovernmental organizations are likely to collect, and do you only need numbers at the whole-country level?
- NO, I need public opinion statistics for a whole country: Try iPoll if you only need statistics for the United States. If it's not there, or if you need statistics for foreign countries, try Polling the Nations. If you can't find what in you need in either of those databases, please talk to a librarian or to a DASIL tutor.
- NO, I need public opinion statistics for smaller areas: Try Polling the Nations. If you can't find the data you need there, please talk to a DASIL tutor or to Julia Bauder [bauderj], the data librarian. They may be able to help you calculate statistics for smaller areas using data from a national survey.
- NO, I need public opinion data: Try Roper Express or ICSPR. These sites can be tricky to search, so if you can't find the data you need please talk to a librarian or to a DASIL tutor for help with searching.
- NO, I need election returns for the U.S.: For historical elections, try CQ Voting and Elections Collection, then America Votes. For more recent elections, your best bet is often to get the data directly from each state's elections bureau, which is usually a subdivision of the secretary of state's office. Using your preferred search engine, search for the name of the state and "secretary of state," then look around the secretary of state's site until you find the election returns. If you can't find the information you need, please talk to a librarian or to a DASIL tutor.
- NO, I need election returns for another country: For recent elections, you can use the search engine of your choice to search for the country's ministry of the interior, which often (but not always) will oversee elections. You may need to be able to read and search in the official language of that country to find the election returns. If you need help, please talk to a librarian or to a DASIL tutor. (Several of the librarians and DASIL tutors can help you search in other languages.)
- NO, I need other numbers at the province/district/state/county level: Go to step 3.
- NO, I need statistics from a small-scale survey or experiment: These statistics are usually found in scholarly articles. If you didn't have any luck finding a scholarly article with the statistics you need in step 1, your best bet is going to be to talk to a librarian about other places to search for articles.
3) Do you need data or statistics for the U.S., for another country, or for multiple countries?
- I need data or statistics for the U.S.: Try the Statistical Abstract (best for whole-country or state-by-state numbers; data is available 1870s-present), American Factfinder (best for small-area numbers, although you can get state and national data; data is available 1990-present), and/or Data.gov. If you still can’t find it, go to step 4.
- I need data and statistics for another country: Use the Statistics – National Agencies and Compendia site to find links to the local equivalent of the Census Bureau and/or the Statistical Abstract. Can you find the numbers there? If not, go to step 4.
- I need data for multiple countries: Go to step 4 for now. If step 4 doesn't work, you can try using the Statistics – National Agencies and Compendia site and checking the statistical agency for each country, but beware! Each country's agency may use different definitions for some concepts, making it problematic to compare the data across countries. Also, if you need more than a few countries, this could be very time-consuming.
4) Look at the subject guide for Statistics and Data Sets. Do you see any likely candidates there? If so, try them. If that doesn’t work, go to step 5.
5) It's probably time to consult an expert. Both librarians and DASIL tutors can help you search for data.