People speak of 'push' and 'pull' factors concerning migration. Push factors are associated with the place of origin. It could be difficulty in finding a suitable job, war, or famine. Pull factors are associated with the place of destination. Most often these are economic, like better job opportunities or the availability of good land to farm. However, the prospect of packing up everything and moving to a new and perhaps very strange environment may appear interesting and challenging to an unmarried young man and appallingly difficult to a slightly older man with a wife and small kids. Similarly, the need to learn a new language and customs may excite one person and frighten another. Regardless of why people move, migration of large numbers of people causes conflict. The United States and other western countries have experienced adjustment problems with each new wave of immigrants. The newest arrivals are usually given the lowest-paid jobs and are resented by native people who may have to compete with them for those jobs. It has usually taken several decades for each group to be accepted into the mainstreams of society in the host country.