Budget-Xfer: Budget-Constrained Source Language Selection for Cross-Lingual Transfer to African Languages

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Main Authors: Idris, Tewodros Kederalah, Eiselen, Roald, Mitra, Prasenjit
Format: Preprint
Published: 2026
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author Idris, Tewodros Kederalah
Eiselen, Roald
Mitra, Prasenjit
author_facet Idris, Tewodros Kederalah
Eiselen, Roald
Mitra, Prasenjit
contents Cross-lingual transfer learning enables NLP for low-resource languages by leveraging labeled data from higher-resource sources, yet existing comparisons of source language selection strategies do not control for total training data, confounding language selection effects with data quantity effects. We introduce Budget-Xfer, a framework that formulates multi-source cross-lingual transfer as a budget-constrained resource allocation problem. Given a fixed annotation budget B, our framework jointly optimizes which source languages to include and how much data to allocate from each. We evaluate four allocation strategies across named entity recognition and sentiment analysis for three African target languages (Hausa, Yoruba, Swahili) using two multilingual models, conducting 288 experiments. Our results show that (1) multi-source transfer significantly outperforms single-source transfer (Cohen's d = 0.80 to 1.98), driven by a structural budget underutilization bottleneck; (2) among multi-source strategies, differences are modest and non-significant; and (3) the value of embedding similarity as a selection proxy is task-dependent, with random selection outperforming similarity-based selection for NER but not sentiment analysis.
format Preprint
id arxiv_https___arxiv_org_abs_2603_27651
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Budget-Xfer: Budget-Constrained Source Language Selection for Cross-Lingual Transfer to African Languages
Idris, Tewodros Kederalah
Eiselen, Roald
Mitra, Prasenjit
Computation and Language
I.2.7
Cross-lingual transfer learning enables NLP for low-resource languages by leveraging labeled data from higher-resource sources, yet existing comparisons of source language selection strategies do not control for total training data, confounding language selection effects with data quantity effects. We introduce Budget-Xfer, a framework that formulates multi-source cross-lingual transfer as a budget-constrained resource allocation problem. Given a fixed annotation budget B, our framework jointly optimizes which source languages to include and how much data to allocate from each. We evaluate four allocation strategies across named entity recognition and sentiment analysis for three African target languages (Hausa, Yoruba, Swahili) using two multilingual models, conducting 288 experiments. Our results show that (1) multi-source transfer significantly outperforms single-source transfer (Cohen's d = 0.80 to 1.98), driven by a structural budget underutilization bottleneck; (2) among multi-source strategies, differences are modest and non-significant; and (3) the value of embedding similarity as a selection proxy is task-dependent, with random selection outperforming similarity-based selection for NER but not sentiment analysis.
title Budget-Xfer: Budget-Constrained Source Language Selection for Cross-Lingual Transfer to African Languages
topic Computation and Language
I.2.7
url https://arxiv.org/abs/2603.27651