Push factors are reason why people leave a country, pull factors are why someone may choose one country over another to immigrate.
There were lots of immigrants from Ireland as there was a large famine. If you want to read a satirical story from the 1700s of how someone proposed to fix the famine in the country click the link below. Be aware this story is untrue, and was written as a joke to make people laugh during a very difficult time. Some content may be sensitive to some readers so do not feel obligated to read it, it is purely for interest sake. http://art-bin.com/art/omodest.html