After ousting the Haitian occupying force from the country, Dominican nationalists had to fight against a series of attempted invasions from 1844 to 1856. Haitian soldiers would make incessant attacks to try to regain control of the territory, but these efforts were to no avail as the Dominicans would go on to win every battle henceforth. Since then, Dominican–Haitian relations have been unstable. In October 1937, claiming that Haiti was harboring his former Dominican opponents, Rafael Trujillo ordered an attack on the border, slaughtering tens of thousands of Haitians as they tried to escape. The number of dead is still unknown, though it is now calculated between 20,000 and 30,000. In the mid-twentieth century, the economies of the two countries were comparable. Since that time, the Dominican economy has grown while the Haitian economy has diminished. The economic downturn in Haiti has been the result of factors such as internal power struggles, rapid population growth, environmental degradation, and trade embargoes. Today, Haiti is the poorest country in the Western Hemisphere. There is a lack of resources, and Haiti's population density exceeds its neighbor's by far. Despite the sending missions since the 1990s, in order to maintain peace, terrible conditions persist. One large contributor to cultural dissonance is the language barrier, as Spanish is the primary language spoken in the eastern part of Hispaniola (Dominican Republic) while French and Haitian Creole are spoken in the western part (Haiti). Race is another defining factor of Dominican–Haitian relations. The ethnic composition of the Dominican population is 73%mixed race, 16%white, and 11%black; while 95% of the Haitian population is black. The Dominican economy is also over 600% larger than the Haitian economy. The estimated annual per capita income is US$1,300 in Haiti and US$8,200 in Dominican Republic. The divergence between the level of economic development between Haiti and the Dominican Republic makes their border the one with the highest contrast of all Western world borders and it is evident that the Dominican Republic has one of the highest illegal migration issues in the Americas. Some cross-border cooperation exists in areas such as health, business, and infrastructure. Many Haitians travel to the Dominican Republic to find seasonal or long-term work in order to send remittances to their families. Some of these Haitian workers, as well as Dominicans of Haitian descent have reported complaints of discrimination against them by the Dominican majority population. Other Haitians who would seek work, instead remain in Haiti, fearing discrimination on the other side of the border.