RT Monograph SR 00 A1 Nguyen, T.H.A A1 Thomas-Agnan, Christine A1 Laurent, Thibault A1 Ruiz-Gazen, Anne T1 A simultaneous spatial autoregressive model for compositional data YR 2019 FD 2019-07 VO 19-1028 SP 13 K1 multivariate spatial autocorrelation K1 spatial weight matrix K1 three-stage least squares K1 two-stage least squares K1 simplex K1 electoral data K1 CoDa. AB In an election, the vote shares by party on a given subdivision of a territory form a vector with positive components adding up to 1 called a composition. Using a conventional multiple linear regression model to explain this vector by some factors is not adapted for at least two reasons. The first one is the existence of the constraint on the sum of the components and the second one is the assumption of statistical independence across territorial units which may be questionable due to potential spatial autocorrelation. We develop a simultaneous spatial autoregressive model for compositional data which allows for both spatial correlation and correlations across equations. We propose an estimation method based on two-stage and three-stage least squares. We illustrate the method with simulations and with a data set from the 2015 French departmental election. T2 TSE Working Paper PB TSE Working Paper PP Toulouse AV Published LK https://publications.ut-capitole.fr/id/eprint/32640/ UL https://www.tse-fr.eu/sites/default/files/TSE/documents/doc/wp/2019/wp_tse_1028.pdf