What does DECIMA mean?

The word ‘decima’ translates literally to ‘one tenth’ in Latin and Italian. The DECIMA Project takes its name from the 1561 decima tax, a 10% property value tax. DECIMA is also an acronym that stands for the Digitally Encoded Census Information & Mapping Archive.


People move, buildings and streets do not

While most digital mapping of pre-modern cities focuses on the built environment, few also integrate comprehensive and comparative sets of city-wide data that include elements like human movement or economic activity.

We built DECIMA to fill this critical gap and to give historians bold new ways to ask important questions. How did Florentine citizens respond to plague, where did they work, what pathways did they highlight for tourists, what sounds did they hear?


Building the database

The DECIMA project uses data from three censuses of the city of Florence from 1551, 1561 and 1632. These three census have slightly different purposes: the first, a descrizione of the city and its inhabitants, allowed Duke Cosimo I de’ Medici to account for his population at the height of his power. The second, a decima property tax, allowed Cosimo to account for his population’s assets. The third, from 1632, allowed Cosimo’s great-grandson, Duke Ferdinando II de’ Medici to account for his surviving population following the major plague of 1630.

These three censuses are preserved in archives and libraries around Florence. You can find them in the Archivio di Stato di Firenze and the Biblioteca Nazionale-Centrale Firenze at the following shelfmarks:

1551: Archivio di Stato di Firenze, Miscellanea Medicea II 223

1561: Archivio di Stato di Firenze, Decima Granducale 3780-3784

1632: Biblioteca Nazionale Centrale-Firenze, Palatino E.B.15.2

Preserving these thorough but unique records with modern, searchable database technology has been challenging. The Decima records were initially plotted in a database using FileMaker. Our basic file was divided in categories or data fields, which were used to provide the frame for manuscript entries. In the creation of the database, there was an effort to standardize the various styles and orthographies of the three scribes, without losing the diversity of the document.


The map

A GIS tool can only be as accurate as the map on which it is based.

Since 16th century Florence predated the precision of today’s high-powered, satellite imagery, the DECIMA team opted for the Early Modern equivalent – in this case, an exceptionally accurate hand-drawn map created by Stefano Buonsignori in 1584. This aerial view of the city allows us to view Florence as contemporaries would have seen it, and provides the perfect foundation for the 1561 data.


The result, a tool as dynamic as Florence itself

DECIMA is a powerful GIS mapping tool that allows historians to explore the city’s evolving urban dynamics like never before.

No other city has as rich a store of human data available before the eighteenth century. By combining a variety of historical census and tax data within a precise, geo-referenced spatial framework, DECIMA creates opportunities for new and dynamic ways to uncover social networks, economic currents, and the sensory life of Florence.

DECIMA is also an interdisciplinary research and teaching tool for scholars of early modern Europe. Researchers can examine data about the inhabitants of sixteenth century Florence such as their professional and economic activities, their living patterns, and the distribution of wealth and power throughout the city.




This project is supported by the Social Sciences and Humanities Research Council of Canada

Archivio di Stato di Firenze

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