Searchmetrics users may experience a slight discrepancy in traffic data displayed in their suite versus traffic data displayed in Google Analytics. This discrepancy stems from how Google Analytics data is calculated for websites with high traffic.
Google Analytics will use sampled data to lessen the lag time for displaying reports in their user interface for views with over 500,000 sessions (25 million for premium).
For example, if a view contains 1,000,000, Google Analytics will take a 50% sample of that data to extrapolate data across the report. This may result in slight differences between Google Analytics data and Searchmetrics data for drilled-down views (page views, for example).
From Google's documentation:
Sampling in Google Analytics (or in any analytics software) refers to the practice of selecting a subset of data from your traffic and reporting on the trends detected in that sample set. Sampling is widely used in statistical analysis because analyzing a subset of data gives similar results to an analysis of a complete data set, while returning these results to you more quickly due to reduced processing time.
When a report is based on data from a large number of sessions, you may see the following notice at the top of the report: This report is based on N sessions.
Searchmetrics uses the account parameters supplied during the integration process to query Google's API for traffic data. This process does not take into consideration any sampled data, since data sampling is only used to speed up Google Analytics user interface. As a result, users may see slight differences in data calculated in the Searchmetrics Suite versus sampled data calculated in Google Analytics.