Google Trends: Terms, Locations, Time Ranges Comparisons

Introduction:

Google Trends includes a function that allows users to compare up to five terms, locations or time ranges. Where this function is used, Google Trends generates a line graph with multiple data lines on it, as well as a bar graph.

Google Trends will also generate a set of "regional interest" tables. However, the scores contained within these tables are not modified as a result of the comparison. In other words, they are the same as if no comparison had been undertake.

Unfortunately, it is not possible to utilise more than one type of comparison simultaneously. Therefore, a comparison of time ranges and a comparison of locations is restricted to a single term.

How Are Scores Calculated?

Comparison of Search Terms:

Scores generated in a comparison of search terms are relative to one another. 

In order to obtain these relative scores, Google Trends compares relative search volume for each term with specified time range. 

If for example, "Search Term A" accounted for 0.0001% of total search queries on 10th January and Search Term B represented 0.00005% of total search queries on the same day, the scores awarded to A and B would be equivalent to 2 - 1. The scaling of the scores between 0 and 100 would depend on how the the relative search volume for both terms on the day compares to the highest relative search volume within the time range. 

The scores contained within the bar graph represent the average score for the terms over the specified time range. 

When a comparison of search terms is undertaken with "global' parameters, the relative search volume that is compared is based on an average derived from all the national relative search volumes.

Read more about comparisons of search terms here: Google Trends - Comparison of Terms.

Comparison of Time Ranges:

A comparison of time ranges calculates scores in a very similar way to a  comparison of terms (described above).

Google Trends calculates the relative search volume for the terms across the different time ranges and then collectively scales the data between 0 and 100.


Comparison of locations:

A comparison between locations generates scores calculated in the same way that "regional interest" scores are calculated. The scores are calculated by analysing:

(1) the popularity of the search term relative to total search within the specific territories

and

(2) the relative popularity of the search term within each specific territory, relative to the other territories.

For more general information on "regional interest" scores read Understanding Google Trends.

Google Trends: What Is Partial Data?

Google Trends offers users highly up-to-date information on the relative popularity of a search. This is indicated by the inclusion of a score for the current month. This score is based on partial data, because the month is not yet complete and therefore, the data is not complete either.

Google Trends calculates all it's "interest over time" scores using the following steps:

• The actual search volume of each day within the time range is compared to the total number of search queries received by Google on the respective days. An average relative daily search volume is then worked out for each month or week. 

• The month / week with the highest average relative daily search volume receives a score of 100. The scores of the remaining months are calculated relative to this.  

In the case of "partial data", scores are based on an interim average relative daily search volume. 

Google Trends tells us that it updates it's information daily. Thus, it is not 100% live. In most instances, the "partial data" score has taken into account search data up to 1 or 2 days before the Google Trends analysis has been conducted.

It is possible to determine precisely which days have been included in the calculation of a "partial data" month, by narrowing the Google Trends search to "past week". This will show which days have been awarded a Google Trends score and which days are yet to be assessed for scores.

For example, if you searched for "ice cream" on 20th April 2013, the score awarded for April 2013 would be based on the average daily search volume up to either 18th or 19th April 2013.  

Any score based on partial data is capable of either rising or falling before the month completes.


Read more about partial data here: Understanding Google Trends

Understanding Google Trends

What is Google Trends?:

Google Trends is a search analysis tool that provides data on the relative popularity of search terms (or websites). Users can input a particular term or set of terms and where there is sufficient data available, Google Trends will generate a line graph, indicating how interest has risen or fallen over a period of time, as well as a table indicating the relative popularity of the search term within specific territories ("regional interest").


Google Trends also allows users to limit the analysis by content type, location, time range and category or compare terms, time-ranges and locations. Analyses parameters can be set to exclude terms or return one set of results based on the cumulative search activity of several terms.

How Does Google Trends Work?:

Where there is sufficient data available, Google Trends awards a score of between 0 and 100 to inputted search terms on a month-by-month / day-by-day basis and on a geographical basis. The meaning of these scores differ according to whether users are looking at "interest over time" or "regional interest".  

Interest Over Time:

The scores awarded by Google Trends on the "interest over time" line graph express the popularity of that term over a specified time range.


Google Trends scores are based on the absolute search volume for a term, relative to the number of searches received by Google.


The scores have no direct quantitative meaning. For example, two different terms could achieve scores of 100 in the same month, but one received 1,000 search requests, whilst the other received 1,000,000. This is because the scores have been scaled between 0 and 100. A score of 100 always represents the highest relative search volume.

Day scores are based on absolute search volume for the term within the day relative to absolute search volume on Google on the same day.  Month / week scores are calculated on the basis of the average relative daily search volume within the month / week. 

A rising line does not necessarily indicate a rise in the popularity. Instead, it may indicate that general search use has increased over the time range. A declining line does not always represents declining popularity either for the same reason. In order to gain the maximum insight from Google Trends, it is necessary to have an understanding of how internet usage might rise or fall.  

The inclusion of scores based on "partial data" is an indicator of just how up-to-date Google Trends is. Read more on partial date here: Google Trends: What Is Partial Data?

It seems likely that Global scores are based on an average score from each country. If this wasn't the case, terms that are popular in countries with high internet usage would constantly perform better than terms that are popular in countries with low internet usage.

Regional Interest: 

The scores awarded by Google Trends on the "regional interest" table / map are not directly relative to one another in a quantitative way. If this was the case, countries or cities with high internet usage or big populations, such as the United States, would permanently find themselves at the top of tables, giving the misleading impression that these countries are "most interested". 

Instead of awarding scores based on direct relativity, Google Trends utilises a kind of "double relativity".  The calculation of scores for particular territories is based on the following data: 

(1) the popularity of a search term within a particular region, relative to the total volume of search within the region over the period specified. 

(2) the relative popularity of the search term for the territory (as determined by step one above) compared to the relative popularity of the search term in other territories.

An example of how regional interest is calculated is given below:


If the search term "Facebook" accounted for 1% of total search requests in the United Kingdom from January 2004 to the present day, but 4% of total search requests in Ireland over the same period, Ireland's score would be 100, relative to the United Kingdom's score of 25.


Ireland's higher score is awarded despite the fact that 1% of total search in the United Kingdom would invariably account for a much higher actual volume of search than 4% of total search in Ireland (given the far higher internet usage / population in the UK).  

As well as generating a simple table, Google Trends also produces a heat map, which shows interest across the globe. The scores shown on the heat map are calculated in the same way that the scores in the table are calculated (ie step 1 and 2 above).