Visual foundation models based on Vision Transformers often depend on large datasets and substantial computational resources, limiting their accessibility for resource-constrained research settings. This paper investigates the data efficiency of Masked Autoencoders (MAE) by studying how pre-training dataset size and mask ratio affect downstream representation quality. An MAE model is pre-trained on nested subsets of the same dataset ranging from 1k to 100k images, using different mask ratios, and then evaluated on a different downstream task dataset. The results show that MAE learns transferable representations even from small unlabeled datasets, with downstream accuracy increasing steadily as more pre-training data is used. The experiments also show that the optimal masking difficulty depends on the data regime: lower masking improves validation accuracy for the smallest subsets, while the original 75% MAE mask ratio becomes stronger as the dataset size increases. These findings suggest that mask ratio should not be treated as a fixed default in MAE training. Instead, reducing the mask ratio can improve data efficiency when pre-training data is limited, while higher masking remains effective when more visual variation is available. ... Read more