Tetradas documents the main results to date of an effort to convert ‘raw’ data in the electronic database of Sound Toll Registers Online (further: STRO, www.soundtoll.nl) for the period 1670-1856 into tonnage estimates.

The collection of files stored here provides all information necessary to assess and replicate the conversion process and contains a selection of annual statistics based on the converted STRO data. The files are regrouped in 9 series. The replication data is stored in the series starting with 9_AUX.

9_AUX comprises: (1) Auxiliary tables containing the original 'raw' data on cargo descriptions, weights and measures, quantities and ports as well as their standardized equivalents, (2) An account of the rules for the conversion of weights and measures in STRO, (3) A step-by-step replication method for "Tetradas: Dataset of tonnage estimates of trade through the Danish Sound, 1670–1856." and (4) A relational database structure containing a sample dataset for the year 1730. The replication method starts from the ‘raw’ data that downloaded from the website of the Sound Toll Registers Online project. Twelve steps describe how to replicate the statistical series of Tetradas using the auxiliary tables in the online documentation. Data from STRO for the year 1730 are used as example. An Microsoft Access database, which contains the 1730 data as well as the different steps of the replication procedure, provides assistance during the replication process.

The selected annual statistics are stored in the series 1 to 8 and cover the following topics: (1) Turnover: Total turnover of trade through the Danish Sound; (2) C: Estimated tonnage of exports from the Baltic and imports from the West; (3) EI: Exports from the Baltic and imports from the West of ports and countries involved in trade through the Danish Sound; (4) T: Total estimated tonnage of transport services provided by ports and countries active in trade through the Danish Sound; (5) BIE: Balances of exports from the Baltic and imports from the West of the main countries active in trade through the Danish Sound; (6) BTR: Bilateral import and export statistics of the main trading partners active in trade through the Danish Sound; (7) PIES: Statistics of exports from the Baltic and imports from the West of a selection of ports active in trade through the Danish Sound; (8) CIES: Statistics of exports from the Baltic and imports from the West of a selection of commodities traded through the Danish Sound.

The readme-file provides information more details about the selection of annual statistics, the abbreviations used and the 'raw' data itself.