How did migrations in this period compare to earlier periods?

"we take the liberty of writing to you again upon the subject of emigration to America for we are quite tired of this country... For the thought of being ushered into the workhouse with our wives and children and the miseries of starvation and poverty make us quite tired of our native land. For we know that we cannot be worse off than we already are. ( 

Migration dramatically increased from 1750 to 1900 due to many factors. 

Work- One of the largest reasons people moved was to find new work when previous occupations failed to provide the necessary wealth required to live life to one's standards. 

Punishment- Sometimes prisoners were forced to migrate such as British criminals who were shipped off to the prison colony of Australia. The Americas became a popular site to send prisoners from Europe as well.

Religion- Europeans grew tired of being forced to follow the official religions of the countries they resided in. Many people escaped their religious obligations by migrating to new places such as the colonies of the Americas which eventually led to the formation of specific religion based states. A perfect example would be the Quakers who largely contributed to the founding of the state of Pennsylvania. 

Thousands of foreigners migrated into the United States during this time period because of all three of these factors. This is what gave the United States its nickname "The Melting Pot".

Overall from the time period of 1750-1900, the world saw a huge amount of migration due to new wealth opportunities such as the California Gold Rush, crime that led to the exportation of prisoners, and religious freedom in the Americas.

Sources:  

Smith, Bonnie G., Marc van de Vieroop, Richard van Glahn, and Kris Lane.

      Crossroads and Cultures: A History of the World's Peoples. United Sates of America: Bedford/

      St. Martin's, 2012. Online.