By my opinion (and I don't want to think much and recall some courses' theories) depends on the linking and dependency of one country's economy to the economy of the USA and the currency interdependancy. Also depends on the currency basket a currency uses for exchange rate.
Countries that do not have fully convertible exchange rates (such as DR) use currency baskets. To achieve full convertibilty, currency must have both internal and external convertibility. Internal convertibility means ability to echange freely from/to foreign currency within a country. External means - outside of country. DR Peso does have internal, but not external convertibility. It also uses a currency basket (mainly comprised of US Dollars. After reading what the currency basket is below, you will understand why the Peso rate has not changed much as compared to dollar as a free (fully convertible) currency (not using a currency basket) would.
Currency basket:
In the context of international exchange, currency baskets are in place particularly as an alternative to the fully convertible (free) rate of exchange in connection to an individual currency. The portion (and importance) of the currencies contained in the basket depends on their meaning for the committing country. The rates of exchange of the domestic currency in relation to the currencies contained in the basket then result proportionally into the rate of exchange of the inland currency to currencies outside the currency basket. A goal of the monetary policy is it to keep the course between inland currency and currency basket constant.
This is an adjusted web translation.
For example, Argentinean Peso has been the same over the last year (May 25, 2006 through May 25, 2007), 3.05 then, 3.08 now. The interlinking between Argentinean and US economy has bene long known, ever since Argentine peso was pegged to dollar at 1:1 up to 2002. Argentina also has internal convertibility, but not external one, and uses a currency basket mainly comprised of US Dollars.
Brazilian Real got appreciated by 10% (2.128 then, 1.98 now).
For FX history, look here
FXHistory - Historical Currency Exchange Rates
For Dominican peso, May 25, 2006 we were at 33.6, today we're at 32.6
All these are interbank exchange rates. For RDP, to get actual rate, discount 0.5 points to 0.6 points from the published rate.
Also, note, Euro appreciated 7% against dollar in last year (May 25, 2006 to May 25, 2007) from 1.27 to 1.36, whereaes about listed Peso rate only adjusted 3%. Compare, however, Brazilian Real that adjusted 10%.
Anyone interested in learning more about exchange rates
Exchange rate - Wikipedia, the free encyclopedia