# Analysis and Aggregation

For aggregating individual level data, best practive is to take a simple average of values for each variable for across each record. However, when aggregating area based data (such as census block groups, the standard format of our geographic file), best practice is to use a weighted average.

## Weighted Averages¶

Weighted averages should generally perform better when aggregating area based data since it will more accurately describe the summary values for a group. The weight that should be used is typically population (or household count).

Many users of our data pair it with mobile movement or visitation data. In this case, visit or visitor count data would also be an appropriate weight.

The formula for a weighted average is shown below.

Multiply each weight by each value across records. Sum these values and divide them by the sum of all weights to produce the weighted average across several areas.