A computational study by researchers in the UK has shown that alkyl groups are inductively electron-withdrawing relative to hydrogen, and not electron-donating as described in some textbooks.

Department of Chemistry, University of Wisconsin─Madison, 1101 University Avenue, Madison, Wisconsin 53706, United States ...

Department of Chemistry, Virginia Tech, Blacksburg, Virginia 24061, United States ...

Changes in the anions (chloride, iodide, bromide, nitrate, bicarbonate, sulphate, phosphate, citrate, and acetate) indicated that the molecular size of the anion rather than its chemical nature was ...