• commute .. in 610610, tanbinvest and gz
• schooling .. mostly in 61060, but SDXQ goes into tanbinvest
• UChicago .. mostly in 610610, but also in tanbinvest and jobjob
• U.S. migration .. mostly in 610610, but tanbinvest covers housing, commute topics
• SG advantage over U.S. or China .. mostly in 610610, sometimes in tanbinvest
• retirement destination .. mostly in tanbinvest, but some country comparisons go to 610610
• absorbency .. split between 610610 and jobjob
• historical reviews ..  a type of blogposts.. can belong to 610610, jobjob or tanbinvest
• brain aging .. mostly in jobjob, sometimes in 610610
• blockchain currency .. split evenly between tanbinvest and jobjob
• salary figures .. salary figures in other blogs

I feel by default, homeless topics belong to 610610.