Many teams run the same survey again as a new survey each quarter or each year. Team Longitudinal Analysis puts those surveys side by side. Each survey becomes one wave, BlockSurvey matches the questions they share, and the report shows how each answer changed and where it is heading over the next waves.
If you want to compare one survey's responses across date ranges instead, see How to Use Longitudinal Analysis & Forecast.
Pre-requisites:
A team workspace with AI features turned on for your organization.
A team role that can view AI Data Analysis reports. To run a new analysis, your role also needs create access.
At least 2 surveys in the team that have responses.
How to Set It Up
In the team sidebar, click Longitudinal Analysis, then click Run Longitudinal Analysis. The Compare Surveys Over Time popup opens.
Surveys: select 2 to 10 surveys. Each row shows the survey's response count. The selected surveys appear on the right as waves, ordered by the date each survey was created. Use the arrows to change the order (oldest first) and edit a wave's name if you want a shorter label, such as Q1 2026. The first survey is the reference, so its questions are the ones the others are matched to. Click Continue to Map Questions.
Map Questions: BlockSurvey matches questions by type, title and answer options. Each match gets a label: Exact, Review options (same question, but some options differ), Similar title, Scale differs (the rating scales are not the same size), Manual or Not found. Hide exact matches is on by default so you only see the rows that need a look. You can pick a different match from the dropdown, click Edit options to pair answer options by hand, or untick a question to leave it out.
Suggest matches with AI is optional. It sends only question text and answer option labels to AI, never responses. Suggestions are marked AI suggestion so you can check them before continuing.
Attributes: check the Analysis name, choose the metrics (Responses, View/Drop Counts, Engagement Metrics) and the questions to include. Questions tagged Personal data start unselected. Click Continue to Forecast Period.
Forecast Period: choose how many future waves to forecast: 1, 2, 3, 5 or 10. Click Generate Longitudinal Analysis.
BlockSurvey then decrypts each survey in your browser, showing progress for each one, compares the waves and saves the report. When it finishes, the report appears in the Reports list on the Longitudinal Analysis page.
Which Questions Can Be Compared
Only question types whose answers can be lined up reliably across different surveys are available. These can be compared:
Choose Single, Choose Multiple, Drop Down Single, Drop Down Multiple, Consent and Ranking
Matrix questions (single, multiple, star, text and number)
Star rating, opinion scale, Slider, Number, Date and List
Short and long text, Email, Phone, Website and Country
File Upload, Image Capture, Signature, Contact Form, Schedule a Meeting, Color Picker, and wallet and social verification questions
These types appear greyed out with the note "This question type can't be compared across surveys yet": Experience Management (NPS, CSAT, CES), MaxDiff, Conjoint, Bipolar, Van Westendorp, Gabor Granger, Cart, Payment, Matrix dropdown, Multiple Textboxes, Multiple Numberboxes and A/B tests.
Questions without a title are not matched automatically. Match them by hand in the Map Questions step if you want them in the report.
Reading the Report
The report uses the same layout as survey-level Longitudinal Analysis. Each wave is labelled with its survey name and response dates, for example "Wave 1 : Q1 feedback (2026-01-05 to 2026-03-28)".
Trend Analysis shows how each answer changed from wave to wave and marks changes that are statistically significant.
Projected Analysis shows the forecast for the next waves, labelled +1 wave, +2 waves and so on, with a likely range.
Individual Reports shows one wave at a time.
Use Show values as: Percentage | Count to switch between percentages and response counts. Hover over a chart to see exact values. When a question has fewer than 30 answers in a wave, a "Small sample" note above it lists the answer count for each wave, so you know which changes to treat with care.
What Uses AI and What Doesn't
The numbers come from statistics, not AI. Percentages, significance checks and forecasts are calculated directly from your responses. With 2 to 4 waves the forecast follows a straight-line trend, and with 5 or more it uses a damped trend model that flattens out over time. The likely range widens the further ahead it looks.
AI is used in three places: it writes the summaries (each one AI wrote carries an AI-written tag), it labels sentiment and themes for open-ended answers, and it suggests question matches when you click Suggest matches with AI. Responses are decrypted in your browser, and only totals and percentages are sent for analysis.
Example: Quarterly Customer Feedback
A support team copies its customer feedback survey at the start of every quarter, so after a year it has four separate surveys. They select all four, keep the order from Q1 to Q4 and rename the waves to Q1 to Q4. Most questions match as Exact. One rating question was changed from 5 to 10 stars in Q3, so it shows Scale differs and they leave it out. They forecast 2 waves.
In the report, Trend Analysis shows which answers moved between Q1 and Q4 and whether each change is significant. Projected Analysis shows where those answers are heading for the next two quarters if the trend holds.
Managing Reports
All team reports are listed on the Longitudinal Analysis page with the number of surveys compared and the date created. Click a report to open it, and use the download icon to export the data as CSV or the tab you're viewing as PDF. To delete a report, click the delete icon and confirm in the popup. Team reports can't be published as public links.
Who Can Use It
Team Longitudinal Analysis follows your role's AI Data Analysis permissions: view to open reports, create to run a new analysis and delete to remove reports. Owners, admins and members have all three by default. Contributors and guests don't see Longitudinal Analysis in the sidebar. If your role can view reports but not run them, the Run Longitudinal Analysis button is greyed out with the note "Your role can view reports but can't run a new analysis."
Tip: Copy the previous survey to create the next one instead of building it from scratch. Copied questions keep the same titles and options, so most of them match as Exact. Use at least three waves for a steadier forecast.