So I was playing around a bit with Gapminder (http://www.gapminder.org/world/#$majorMode=chart$is;shi=t;ly=2003;lb=f;il=t;fs=11;al=30;stl=t;st=t;nsl=t;se=t$wst;tts=C$ts;sp=0.1;ti=1882$zpv;v=0$inc_x;mmid=XCOORDS;iid=phAwcNAVuyj0TAlJeCEzcGQ;by=ind$inc_y;mmid=YCOORDS;iid=phAwcNAVuyj2tPLxKvvnNPA;by=ind$inc_s;uniValue=8.21;iid=phAwcNAVuyj0XOoBL_n5tAQ;by=ind$inc_c;uniValue=255;gid=CATID0;by=grp$map_x;scale=lin;dataMin=0.836;dataMax=9.2$map_y;scale=lin;dataMin=18;dataMax=87$map_s;sma=49;smi=2.65$cd;bd=0$inds=), and noticed that in 1882 icelands life expectancy dropped dramatically to 18 years only to pretty much immediatly recover. I know the webpage says "data before 1900 is highly uncertain" but don't researchers in that case normally try to mkae the modest of guesses? Or is it a faulty number that has snuck in? Or was it some kind of known plague or something going on then?
This might help: http://gcanyon.wordpress.com/2009/06/25/life-expectancy-in-the-1800s-not-as-bad-as-reported/
On that page the writer cites a peg about the general life expectancy globally. It seems due to Infant mortality rates at the time, life expectancy became inaccurate to a degree. Once a child had aged passed 10 the chances of living past 50 greatly increased.