C.1. Good practices in using external party sources
10.49. External party sources have some inherent limitations. While they can provide insights and perspectives than not available more traditional sources, compilers should be aware of the unique challenges of using statistics compiled by non-statistical entities.
10.50. Most importantly, external party sources vary in terms of data quality and timeliness, which ultimately depend on the quality of the statistical processes of the external party. It is recommended that the compiling agency become as familiar as possible with the data sources, collection methods, methodology and statistical rigor of the external institution and document its strengths and weaknesses. It is strongly recommended that the compiling agency contact the external source directly to discuss such issues in greater detail, to alert the data provider that its data may be used for official purposes and to open the lines of communication so that any changes in methodology or timeliness can be transmitted to the compiling agency in a timely manner. Some external parties may be willing to work more closely with the compiling agency in order to better meet the official statistical requirements; however, even in such an instance, the national statistics office should continually monitor the quality of the data and be aware of the limitations and weaknesses.
10.51. The compiling agency should assess whether the data available from the external party helps to provide statistics on the trade in services category of interest, or other types of statistics related to the international supply of services. In many cases, the definition of the industry or other aspects related to the international supply of services does not match the official statistical definitions. Such misalignments may lead to misinterpretations and misuse of the data. Again, it is strongly recommended that the compiling agency learn all such definitions and methodological aspects of the external party source.
10.52. Timeliness and frequency are common weaknesses of external party sources. The compiling agency should be prepared for breaks in series, changes in methodology, changes in survey sample sizes and even the disappearance of the source. In particular, it is recommended that the compiling agency develop plans for cases in which there is a reasonable expectation that the external party source might substantially change or disappear. It may be advisable to use an infrequent data source as an input to a data model that estimates the value of service transactions, or to interpolate missing years or to fill other data gaps, rather than relying solely on that data source.
10.54. It is further advised that compiling agencies appropriately document all data sources in the metadata, including in which years the data source was used, and to keep documentation on the external party source, including historical data, revisions, methodological documents, communication and any user agreements.