A semigroup \documentclass[12pt]{minimal}
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\begin{document}$${\mathfrak{S}}$$\end{document} of non-negative n × n matrices is indecomposable if for every pair i, j ≤ n there exists \documentclass[12pt]{minimal}
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\begin{document}$${S\in\mathfrak{S}}$$\end{document} such that (S)ij ≠ 0. We show that if there is a pair k, l such that \documentclass[12pt]{minimal}
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\begin{document}$${\{(S)_{kl} : S\in\mathfrak{S}\}}$$\end{document} is bounded then, after a simultaneous diagonal similarity, all the entries are in [0, 1]. We also provide quantitative versions of this result, as well as extensions to infinite-dimensional cases.