Does the percentage of Zakat due on money need revision?

The prescribed percentage for Zakat on wealth is one-quarter of one-tenth (2.5%), and the proof for this is the hadith of Anas reported by Al-Bukhari: "On silver, one-quarter of one-tenth." And likewise, the hadith of Aisha and Ibn Umar reported by Ibn Majah: "The Messenger of Allah would take half a dinar from every twenty dinars, and one dinar from forty dinars."