THE "feelgood factor" of a buoyant economy is starting to have an effect on the number of births and marriages, according to the latest figures from the Central Statistics Office.The number of births in the third quarter of 1997 was the highest July-September figure for 10 years, according to the CSO.Births in that period were up for the fourth year in a row. There were 14,411 registered between July and September, which has taken over from the second quarter as the year's most fecund season. This was 1.1 per cent up on the corresponding period last year. The annual birth rate has been rising since 1994 after falling by nearly 20 per cent since 1980.The marriage rate also increased in the third quarter of 1997, with 7,011 marriages representing a 0.4 per cent increase over the same period in 1996. This is the first thirdquarter increase since 1992, although in the longer term the marriage rate continues to fall steadily. To complete the happy picture in the summer of 1997, the death rate was 0.3 per cent below the corresponding quarter of 1996.Prof Jerry Sexton of the Economic and Social Research Institute said `buoyancy in the economy" was a factor making families decide to have an extra child. "People's expectations are that things are getting better," he said. Another factor in the higher birth rate was the 15,000 people who had migrated or returned to Ireland in the year to April 1997. Many of these were just the kind of 23- to 35year-olds who were most likely to get married and have children.This inflow - up from around 8,000 in 1995-96 and zero in previous years - together with a 19,000 natural increase, meant a rise in the State's population of around 34,000 in 1996. Prof Sexton said it was too early to talk about a permanent turnaround in the birth rate. Most demographers believe this will depend on the longer-term economic situation.What some see as the more negative side of contemporary Ireland is illustrated by the CSO's figures for the continuing and dramatic increase in the number of births outside marriage. Some 26.2 per cent of total births in the third quarter of last year were outside marriage, compared to 24.8 per cent in the whole of 1996, 14.5 per cent in 1990 and 8.5 per cent in 1985.