One of the most difficult questions you’ll have to answer when media planning is, “what’s the cumulative reach?” 😱

Here are 10 different ways to estimate cumulative reach, including the Total Overlap Method.

What is Cumulative Reach?

“Cumulative Reach” is the de-duplicated count of the number of unique people reached by all the placements in your media plan, collectively.

Pop Quiz on Cumulative Reach

Suppose you have a media plan with four placements. Each of the media placements reaches a certain number of people as follows:

Placement Reach
1 655,404
2 4,581,873
3 2,830,155
4 1,394,224

How many people will you reach with this media plan?

Beware, this is a trick question!

You Can’t Just Add It Up …

You might be tempted to simply add up the Reach column, which amounts to 9,461,656.  But that would be naïve because it assumes there is no overlap between the placements.

… Because There’s Overlap!

A media plan usually aims to reach a group of people with similar characteristics. As a result, it’s likely each of these placements will reach some of the same people as the other placements.

Someone who is exposed to ads from placement 1 may also be exposed to ads from placement 2, placement 3, or placement 4.

How to Avoid Double-Counting

In calculating the number of unique people reached by the media plan – known as “cumulative reach” – you need to eliminate this overlap to avoid double-counting people.

There’s No “Right” Way to Estimate Cumulative Reach

Calculating cumulative reach is not an exact science. The best you can do is estimate.

There are many ways to estimate cumulative reach using statistical models.

Yunjae Cheong’s PhD Thesis

Yunjae Cheong’s excellent University of Texas PhD thesis “Multivariate beta binomial distribution model as a web media exposure model” compares nine different models:

  1. Binomial Distribution Model (BIN)
  2. Beta Binomial Distribution Model (BBD)
  3. Hofmans Beta Binomial Distribution Model (HBBD)
  4. Dirichlet Multinomial Distribution Model (DMD)
  5. Canonical Expansion Model (CANEX)
  6. Conditional Beta Distribution Model (CBD)
  7. Morgensztern Sequential Aggregation Model (MSAD)
  8. Hyper Beta Distribution Model (HBD)
  9. Multivariate Beta Binomial Distribution Model (MBD)

Impractical Cumulative Reach Models

These models are complex and require confusing inputs.

As a result, they are not practical for everyday media planning because media planners cannot supply the inputs required by these models.

For example, here’s the formula for the Dirichlet Multinomial Distribution Model:

Even with software to perform the calculations, it’s a major challenge for a media planner to supply all the parameters required by the equation.

Bionic Employs the Total Overlap Method

To make estimating cumulative reach more feasible in everyday media planning, Bionic employs the Total Overlap Method (TOM) in its media planning software.

A Practical Cumulative Reach Model

The best feature of TOM is it requires only a single, easy-to-understand input – the percent overlap between any placement and all other placements.

Another benefit of TOM is the resulting cumulative reach is guaranteed to be in the range of reasonable estimates (many of the other methods cannot guarantee this).

How the Total Overlap Method Works

Bionic automatically calculates cumulative reach in the summary line of your media plan:

How to Adjust the Overlap

In the example above, the overlap is set at 20%. You can change the overlap by clicking the gear icon:

The calculations get more complex when your media plan is comprised of packages and flighted placements. However, TOM is always easy to understand and can be verified without an advanced math degree.

How to get the Cumulative Reach Tool

If you’re already using Bionic for Agencies, you already have the new cumulative reach tool. The next time you log into Bionic, you’ll find the cumulative reach estimate in the summary row of each of your media plans along with the overlap control.

If you’re not yet on Bionic, you can learn more and start a trial on our website.