Why does histogram packing improve lossless compression rates?

Paulo Jorge S. G. Ferreira, Armando J. Pinho. Why does histogram packing improve lossless compression rates?. IEEE Signal Process. Lett., 9(8):259-261, 2002. [doi]

@article{FerreiraP02-0,
  title = {Why does histogram packing improve lossless compression rates?},
  author = {Paulo Jorge S. G. Ferreira and Armando J. Pinho},
  year = {2002},
  doi = {10.1109/LSP.2002.803018},
  url = {https://doi.org/10.1109/LSP.2002.803018},
  researchr = {https://researchr.org/publication/FerreiraP02-0},
  cites = {0},
  citedby = {0},
  journal = {IEEE Signal Process. Lett.},
  volume = {9},
  number = {8},
  pages = {259-261},
}