Egypt earns most of its foreign income from what are, in effect, rents from sources such as oil, plus tourism, Suez Canal tolls, migrants' remittances and external aid.

ECONOMIST: Egypt's economic misfortunes, miseries and mistakes

Egypt's sickly economy is showing renewed signs of vigour, not least because of tolls from warships heading for Iraq through the Suez canal.

ECONOMIST: A high oil price will delay reforms

But as the canal reaches its full capacity over the next few years, delays will mount, and tolls will probably rise.

ECONOMIST: The Panama canal