New methods increased the value added.

The petroleum industries are large and relatively new in Norway, but Statistics Norway's annual statistics for these industries - the oil statistics - consisted until 2016 of short time series that did not give a comprehensive picture of their development.

The data base and calculations in the oil statistics were changed several times throughout the history. This initially provided statistics that could better describe the petroleum industries, and which covered several types of oil business. Later, reducing the response burden for the business sector and adaptions to the national accounts became more important. The changes also meant that the reference years were not calculated using equal methods, and it was uncertain how comparable they were.

Now, for the first time, historical and comparable time series have been established for the key figures in the oil statistics - employment, labour costs, production value and cost, value added and investments - where the microdata is prepared for analysis.

The historical time series cover the industries:

• extraction of crude oil and natural gas
• oil and gas services
• pipeline transport

They cover the entire period from 1965 to 2017, with microdata covering the period up to 2014 and back as far as microdata was found. For the service industry this was 1972, and somewhat later for the other petroleum industries. To complete the time series, key figures from the national accounts and an older historical oil statistics have been collected for the oldest reference years. In 2015 the oil statistics were heavily modified, and from this reference year onwards only the key figures were collected, as well.

The historical time series are essentially free of breaks. However, two adjustments to the service industry after 2009, resulting from changing population boundaries, cause breaks that must be considered when analysing the time series.

The oil statistics now consist of the new historical time series. The time series differs from the old oil statistics at several points up to 2014, due to recalculation and correction of the micro data:

1. Consumption of goods and services – intermediate consumption - was sharply adjusted between 1981 and 2011, because internal deliveries are no longer counted.
2. The production value has been adjusted significantly - mainly down – because internal deliveries are no longer counted, whereas recalculations based on new data counteract this decrease.
3. The value added has been adjusted up, a consequence of new data in the estimation of production value.
4. Investments have been adjusted up due to changed definitions.

Accumulated through all the years, the value added in oil and gas extraction has been adjusted upwards by NOK 219 billion in 2017, and investments by NOK 116 billion.