With a steadily weakening Euro, the US dollar is worth more than it was last year, and so Apple changed the minimum app price to €0.99 in the EU. They also changed the new minimum prices to £0.79 in the U.K and $1.19 CAD in Canada. Several sources are describing those as increases, although I haven't been able to confirm if that is true.
Unlike Amazon and other retailers that change prices on the fly, Apple, periodically changes their minimum prices to reflect exchange rates. The changes are usually made on a global scale across most if not all iTunes sites, but this latest one is being reported as only affecting Europe and Canada. I'm not sure why Canada was included, but the Euro change may have been triggered by the recent VAT changes.
I don't know that Apple has a set schedule, but I suspect that they also take future exchange rates into account. Apple has now priced apps in euros at parity to the USD price, while the actual exchange rate is around $1 to 1.18 euro. Monetary experts are expecting the dollar and the euro to achieve parity by 2017, and I think Apple is anticipating that day.
Last Wednesday Apple also sent out an email to announce the change. From Talking New Media:
Within the next 36 hours, prices on the App Store will increase for all territories in the European Union as well as in Canada and Norway, decrease in Iceland, and change in Russia. These changes are being made to account for adjustments in value-added tax (VAT) rates and foreign exchange rates.
We will simultaneously update the Pricing Matrix in Rights and Pricing in My Apps on iTunes Connect.
We will also update the iOS Paid Applications and Mac OS X Paid Applications agreements, which will be available in Agreements, Tax, and Banking.
If you have any questions, contact us.
The App Store team