The United Kingdom and Germany have seen major

which includes both the explicit costs, the ticket price, and the implicit cost, lost work time and loss of community ties, also play a major role in the pull of emigrants away from their native country. As transportation technology improved, travel time and costs decreased dramatically between the 18th and early 20th century. Travel across the Atlantic used to take up to 5 weeks in the 1700s, but around the time of the 1900s it took a mere 8 days. When the opportunity cost is lower, the immigration rates tend to be higher. Escape from poverty (personal or for relatives staying behind) is a traditional push factor, the availability of jobs is the related pull factor. Natural disasters and can amplify poverty-driven migration flows. This kind of migration may be illegal immigration in the destination country (emigration is also illegal in some countries, such as North Korea, Myanmar, Zimbabwe, and Somalia).