What is a Group in IMPLAN? Why Groups are More Important Than You Think

WHAT IS A GROUP?

A Group is the part of an IMPLAN Project that connects one or more Events to a particular Region, Data Year, Dollar Year, scaling treatment, and set of Group-level modeling rules.

The basic structure of an IMPLAN analysis consists of three components:

1. The Event describes the economic activity being modeled.
2. The Group establishes the shared analytical environment.
3. The Project contains the analysis.

An Event by itself is not yet a complete economic scenario and a Group is not the economic shock itself.

The Events describe the activity being modeled. The Group establishes the common environment in which those Events are evaluated.

That environment can include:

• Geography
• Data Year
• Dollar Year
• Scaling
• ICA restrictions
• MRIO relationships

The analyst should not interpret results as simply the impact of an event. Rather, a complete interpretation provides the impact of this Event under this Group's economic conditions.

For example, if you move the Event to another Region, you change its economic surroundings. If you change the Group Scaling Factor, you change its magnitude. If you place it beside an ICA Event, you may change its modeling treatment. If you connect its Group through MRIO, you allow regional spillovers to be traced.

The Event tells IMPLAN what happened, while the Group tells IMPLAN what world that Event happened in.

WHY AN EVENT IS A PARTIAL ANALYSIS

Suppose festival organizers have developed a $2,000 visitor-spending profile consisting of lodging, meals, transportation, and entertainment for the Heartland Food and Music Festival occurring in Missouri. 

When adding an Event to the Impacts page, the analyst models a change in economic activity. The Event prompts the analyst to ask, “what economic activity changed?”

However, several unanswered questions arise: 

1. Where was the festival? 
2. Are the spending estimates expressed in 2026 dollars?
3. Which year of the regional economy should represent the economy receiving that spending?
4. Does the $2,000 profile represent one visitor group—or 5,000?
5. Should every Event in the analysis be subject to the same modeling rules?

Although the analyst created the Events, they do not yet know what impacts these Groups generate. The analyst must determine under what shared economic conditions should the Events be analyzed.  Understanding the economic conditions of your Events is essential because the same Event can behave differently when its economic address changes.

A GROUP PROVIDES YOUR EVENTS WITH AN ECONOMIC ADDRESS

You are modeling the economic impact of visitor spending for the Heartland Food and Music Festival analysis and have already built your Events.

The Events consist of: 

1. Hotel spending
2. Restaurant spending
3. Transportation
4. Entertainment

Your regional Heartland Food and Music Festival analysis is not finished, because IMPLAN still does not know where any of this happened, when it happened, or which economic rules should apply to those Events together.

A Group supplies the Data Year, Dollar Year and Geographic Region the event occurred. Events tell IMPLAN what happened. Groups tell IMPLAN where, when, and under what shared modeling conditions it happened.

Events describe the activity to be modeled. A Group establishes the economic context in which those Events will occur.

A GROUP CONNECTS YOUR EVENTS TO ECONOMIC CONTEXT

Four basic Group settings establish the economic context of an Event:

1. Region (Where did the event take place?)
2. Data Year (What was the structure of the economy at that time?)
3. Dollar Year (What year are these dollars worth?)
4. Scale (How much of this activity took place?)

REGION: WHERE DID THE EVENT TAKE PLACE?

The Region identifies the geographic economy receiving the activity. Depending on the analysis, that might be a:

• County
• State
• ZIP Code
• MSA
• Combined Region
• Customized Region

Why does Region matter?

Because the $2,000 festival-spending pattern does not generate some universal impact of $2,000. It interacts with that particular economy in which that spending occurs. If the analyst places the same Events in another regional Group, the spending pattern can remain identical while the receiving economic structure changes.

An Important Geography Rule to Follow

Standard Regions can be selected directly when configuring a Group. However, Combined and Customized Regions must already exist. They cannot be created or modified directly from the Group panel on the Impacts screen.

If your analysis requires one, build it from the Regions screen first. Then select it for the Group.

DATA YEAR: WHAT WAS THE STRUCTURE OF THE ECONOMY AT THAT TIME?

The Data Year identifies the underlying IMPLAN dataset used to represent the Region. The Data Year prompts the analyst to understand which version of this particular economy is being modeled. 

The Data Year establishes the economic relationships and the Social Accounting Matrix used for the analysis.

DOLLAR YEAR: WHAT YEAR ARE THESE DOLLARS WORTH?

The Dollar Year identifies the currency year of the values entered into your Events. It prompts the analyst to determine what year's dollars the values expressed are in.

Note: Dollar Year and Data Year do not have to match. When they differ, IMPLAN uses the Dollar Year to determine the appropriate deflator needed to adjust the Event values to the model's Data Year.

SCALE: HOW MUCH OF THIS ACTIVITY TOOK PLACE? (ONE RECIPE, MANY SERVINGS)

Consider the Heartland Food and Music Festival, again. Suppose you surveyed 500 people which averaged a $2,000 visitor-spending profile.  We want our model to reflect the economic activity of all 5,000 visitors to the area, not just the limited group we surveyed. 

To do this, we can either multiply every Event individually or scale the entire Group. Since all Events in our study need to be scaled by the same amount, we will scale the entire group. Simply click the lock icon to unlock the Group Scaling feature and enter a Scaling Factor of 5,000. IMPLAN multiplies the Event Values assigned to that Group by the factor.

Note: The Events describe the recipe. The Group decides how many servings to make.

This works because IMPLAN is a linear model. Analyzing $100 of an activity produces the same modeled relationship as analyzing $1 and multiplying that result by 100.

Group Scaling applies that same principle to the Events in the Group at once. 

A Group Scaling Factor multiplies the Event Values assigned to the Group together, making it useful for repeated units of activity.

Watch for double scaling

Events can also have their own scaling factors. If both Event-level and Group-level scaling are applied, the two factors compound. Suppose an Event is scaled by: 3,000 and the Group containing it is scaled by: 5

The effective scale becomes: 3,000 × 5 = 15,000. If you forgot that the Event had already been scaled, your analysis can become much larger than expected. Whenever Group Scaling is used, check the Event-level scaling too.

Do not scale at both the Event level and the Group level. 

HOW DO YOU BUILD AN IMPLAN GROUP?

While the only place you can modify all components of a group is the Impacts page, there are several paths to getting there: 

1. Start from the Regions Page: This method allows you to select Regions to add to your project from the map or list view.  It also allows you to pick a Data Year for your Group.  Note that the Data Year should be selected prior to selecting Regions. Once you've selected the Data Year and Regions click "ADD TO IMPACTS" to move to the Impacts page. 
2. Start from your Projects Page: If you want to use an Industry Aggregation different than the default Industry Aggregation, you should start a project by clicking "NEW PROJECT" from the Projects page. This will allow you to set the Industry Aggregation, before moving you to Regions page. 
3. Start  from the Impact Page: The Groups panel on the Impacts page allows you to set all components of a Group, as well as add new Groups to a Project. 

For our festival example, we'll start from the Impacts page. Suppose we have already created the Events representing the $2,000 per-visitor spending profile. By default, our Project starts with a single "empty" group included. 
 

There are two required pieces of information we must provide for setting up our Group:

1. Select the Region using the Region dropdown menu. 
2. Give our Group a title. 

In addition, there are three optional steps:

1. Change our Dollar Year if it differs from the default. 
2. Change our Data Year if it differs from the default. 
3. Set the group Scaling factor. 

Once we create our Group we assign Events to the Group. This tells IMPLAN to analyze the activity in our Events, in the economy specified by our Group.

To add an Event to a Group, drag and drop the events in the Group on the right of the Impacts page.

CAN I HAVE MORE THAN ONE GROUP FOR THE SAME REGION?

Yes. Multiple Groups can point to the same Region.

For example, you might want separate Groups for:

• Construction and operations
• Two different Dollar Years
• Two different Data Years
• Alternative modeling treatments
• Simply distinct analytical components that you want to filter separately later

When Groups use the same Region, they must be distinguishable by a different Data Year, different Dollar Year, or unique Group name. Remember, a Group does not show one geography, but one shared analytical environment.

Two Events can occur in the same county and still belong in separate Groups if they require different analytical treatment.

Same region, different groups

Suppose the festival organizers are also building a permanent performance venue in Missouri. 

Both the construction activity and the festival’s ongoing operations occur in the same Region: Missouri. But they represent different parts of the project and should be kept analytically distinct. Therefore, we will add two more groups to represent Construction (Group 2) and Operations (Group 3) for a total of three Groups (including the previous Visitor Spending Group) 

1. Group 1: Visitor Spending - Heartland
2. Group 2: Venue Construction
3. Group 3: Venue Operations
    

Multiple Groups can use the same Region when you need to distinguish different time settings, analytical treatments, or components of a Project.

KEEPING GROUPS ORGANIZED

Groups can be managed directly from the Impacts screen including: 

• Adding groups: Click the button on the top, right corner of the screen to add a group. 
• Duplicating groups: Click on the three dots on top, right corner of the Group card.
• Deleting groups: Click on the three dots  on top, right corner of the Group card.

More Options

PUTTING IT ALL TOGETHER & RUNNING THE ANALYSIS

Building groups ties into the basic workflow of your analysis. The process is straightforward:

1. Build the Events

Begin with the economic activity you want to model. For our festival, that might include Events representing:

• Hotel spending
• Restaurant spending
• Transportation
• Entertainment
• Venue Construction
• Festival Operations

At this stage, you are defining what happened.

2. Create the Group 

Create a Group representing the common analytical environment for those Events.

Select the appropriate:

• Region,
• Data Year
• Dollar Year
• Scale
• Group Name

At this stage, you are defining the economic context for your events. 

3. Assign the Events

Place the relevant Events into the Group. This connects the economic activity to the environment in which it will be analyzed.

4. Review the Group as a Whole 

Before running the analysis, do not review only the individual Event cards.

Ask:

• Should these Events occur in the same Region?
• Should they use the same Data Year?
• Are their entered values associated with the intended Dollar Year?
• Should the same modeling rules apply to every Event in this Group?
• Is Group Scaling being used?
• Is MRIO being used?
• Does the Group contain an ICA Event?

5. Run the Analysis 

When everything reflects the intended scenario, run the analysis and review the Results. Interpret the output as the result of these Events + this Region + this time context + these Group-level settings and rules.

THINK ABOUT GROUPS ANALYTICALLY RATHER THAN VISUALLY

A Group certainly helps organize an IMPLAN Project, but treating it as an ordinary folder invites analytical mistakes.

Remember:

• Events define the economic activity being modeled.
• Groups establish the shared economic environment for those Events.
• Region determines where the activity enters the economy.
• Data Year identifies the economy being represented.
• Dollar Year identifies the currency year of the Event values.
• Multiple Groups can use the same Region when their settings or analytical purposes differ.
• Group Scaling multiplies the Event Values assigned to the Group.
• Event and Group Scaling Factors compound.
• Group names can later be used to isolate components on the Results screen.
• The Event Template can create and map Groups for large analyses, but its formatting rules must be followed carefully.

Groups go beyond the question, “which Events belong together?” to determine “which Events should share the economic scenario that I am modeling?”

CONCLUSION

Our festival began as a collection of visitor spending Events such as: Lodging, Meals, Transportation and Entertainment

Those Events told IMPLAN what changed, while the Group supplied the rest of the analytical world around them.

It told IMPLAN where the activity occurred,  identified which economy represented that place, established the currency context of the entered values, scaled the activity from one visitor profile to thousands and gave us a way to separate pieces of the story again when we reached the Results.

Groups matter more than they first appear, because while an Event tells IMPLAN what happened, a Group tells IMPLAN where, when, at what scale, and under which shared modeling rules it happened.

RELATED ARTICLES

Overview of Regions

Which Year Is It Anyway? Data Year, Model Year, and Dollar Year 

Scaling Groups & Events

Written August 14, 2026