There are three methods of using Google Trends to make comparisons and each of these has filters that improve the analytical capacity of the tool:
Perhaps most basically, users can focus on one or more search term and filter by type of search, location of person making the search, date and category.
Alternatively, it is possible to select one or more locations of people making searches, compare the interest in a specific search term in these places and filter by type of search, date and category.
Finally, users can choose one or more time range (for example, individual years or months), compare the interest in a search term in these periods and filter by type of search, location and category.
Each of these methods produces a chart of 'interest over time', details of interest by area (country, sub-region or city) and lists of the top and rising search terms that relate to the selected term.
The time chart compares search terms, locations of those making searches or time periods, depending on the option selected.
Figures 1, 2 and 3 in the pdf download are examples of parts of the outputs from each of the three methods.
Figure 1 illustrates the proportion of UK searches for all aspects of travel relating to a particular London attraction, Kew Gardens.
This has been decreasing slightly in the years from 2004 to date.
The chart also shows how such interest is most prevalent in the spring months.
Google Trends users are given an option to include forecasts which are shown in Figure 1.
These are only based upon the trends shown rather than any other, external, considerations.
Figure 2 shows an analysis of the search term 'Cardiff' from January 2007 onwards, restricted to the travel category and to searches from three European countries.
The chart illustrates that, generally, interest has been proportionally greater in the Netherlands than in France and Germany.
The most notable of the exceptions to this pattern was in the autumn of 2007 when Cardiff hosted a Rugby World Cup quarter final that included France.
Other spikes in interest in France also coincide with international rugby matches in Cardiff.
The spikes in interest from the Netherlands are not as easily explained by sporting events but a lot of fluctuations in such data are likely to be due to the fact that the information is based on relatively small volumes of searches.
Despite these fluctuations, this particular analysis from Google Trends has clear potential for targeting and monitoring the effects of overseas marketing activity.
Figure 3 again focuses on Kew Gardens, comparing each of the last four full years of the data in Figure 1.
This replicates the seasonality in the proportion of searches that was shown in the previous chart but includes more detail.
Patterns relating to public holidays and the periods outside of school terms are noticeable but other peaks may relate to special events, marketing campaigns or news stories and this type of chart is a useful measure of the impact of such publicity.
The travel category used in these and other analyses in this pages includes sub-categories relating to hotels and accommodation, attractions and activities, bus and rail travel, air travel, car rental and taxis, cruises and charters, adventure travel and vacation destinations.
Google Trends allows users to select these sub-categories and use them in the same way as categories.
Figures 20 and 21, for example, chart the hotel and accommodation sub-category.