Read the section on emigration on Irish Genealogy Toolkit
https://www.irish-genealogy-toolkit.com
Genealogy>Emigration
Page 2 about emigration in 19th century. It says there were 3 distinct phases.
That's interesting information. I haven't see these figures before.
But they raise more questions. For example, emigration from Tipperary decreased sharply between 1857 and 1858, but increased 18% from 1858 to 1859, and by 33% from 1859 to 1860. I wonder what caused the decrease and subsequent increase.
Looking again at the chart, figures for Tipperary seem to mirror the pattern for the rest of Munster. Each province had its' own pattern.
The page "Irish immigration to America 1846-early 20th century" on Irish Genealogy Toolkit suggests 2 factors influencing fluctuations, first a downturn of industrial expansion U.S. in mid 1850s and secondly steamships.
"Steamship Competition
After 1855 the tide of Irish immigration levelled off. However the continuing steady numbers encouraged ship builders to construct bigger vessels. ….. shipowners began to realise economic advantages of specialising in steerage passengers." Conditions onboard improved, fares were often lower than on sailing ships and voyage times reduced to a fortnight. "The concept of Irish immigration to America …. seemed less permanent."
(My English-born aunt's Irish grandparents went to U.S. for a few years in 1860s, had 2 sons there, one my aunts father, then crossed the Atlantic again and settled in England.)
Economic conditions in U.S. and steamships were only 2 factors. As Drosybont said in reply #1 you have to think of "push and pull" factors. Emigration/immigration/migration are complex. There are no simple answers. One has to consider: economic conditions and employment opportunities in Ireland, Britain, Canada, U.S.A., Australia; transport (costs, time, convenience); existing Irish communities in the destination countries; politics; religion.
There's plenty written about the subject.
Many Irish newspapers are online and extracts from some are on various websites. These are interesting for contemporary accounts of events. You need to be aware of political bias of some newspapers when reading them.
See also the pages on Irish immigration to Britain on Irish Genealogy Toolkit. Most convenient, quickest and cheapest choice was to work on the British mainland.