?url_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Adc&rft.relation=https%3A%2F%2Fpure.iiasa.ac.at%2Fid%2Feprint%2F4515%2F&rft.title=Population%2C+Households%2C+and+CO2+Emissions&rft.creator=MacKellar%2C+F.L.&rft.creator=Lutz%2C+W.&rft.creator=Prinz%2C+C.&rft.creator=Goujon%2C+A.&rft.description=In+this+paper%2C+the+Income-Population-Affluence-Technology%2C+or+I%3DPAT%2C+model+is+reformulated+in+terms+of+households+(i.e.%2C+I%3DHAT)+as+opposed+to+persons.+Such+an+approach+is+preferable+in+the+case+of+environmental+impacts%2C+such+as+CO2+emissions%2C+which+are+caused+by+activities+such+as+residential+heating+and+automobile+transport%2C+for+which+there+exist+significant+household-level+economies+of+scale.+%0D%0A%0D%0ABecause+of+historical+changes+in+average+household+size%2C+the+IHAT+identity+gives+rise+to+a+very+different+decomposition+of+the+sources+of+growth+in+environmental+impacts+than+does+the+IPAT+identity.+Taking+growth+in+commercial+energy+consumption+as+an+example%2C+we+find+that+the+IPAT+identity+attributes+18.2%25+of+the+annual+increase+(in+absolute+terms)+over+the+period+1970-90+to+industrialized-country+demographic+increase%2C+whereas+the+IHAT+model+attributes+41.5%25+because+of+the+significant+decrease+of+mean+household+sizes.+The+difference+between+the+two+decompositions+is+simply+that%2C+in+the+first%2C+it+is+the+individual+who+is+the+demographic+unit+of+account%2C+whereas+in+the+latter%2C+it+is+the+household.+%0D%0A%0D%0ABased+on+the+IIASA+world+population+projections+and+derived+projections+of+households%2C+the+IPAT+and+IHAT+identities+are+employed+to+project+the+level+of+CO2+emissions+in+the+year+2100.+In+the+case+where+the+level+of+emissions+per+demographic+unit+is+assumed+to+remain+constant+at+1990+levels%2C+the+IHAT+projection+for+2100+is+over+40%25+higher+than+the+IPAT+projection%3B+in+the+case+where+emissions+per+demographic+unit+are+projected+to+increase+over+rime%2C+tine+MAT+projection+is+over+80%25+higher.+%0D%0A%0D%0AWe+conclude+that+decomposition+and+projection+exercises+are+very+sensitive+to+the+unit+of+account+chosen.+Should+the+unit+of+analysis+be+the+individual%2C+the+household%2C+the+community%2C+or+what%3F+Until+more+is+known+about+the+nature+of+the+many+activities+which+give+rise+to+environmental+impacts+--+specifically%2C+the+role+of+economies+of+scale+--+it+is+unwise+to+draw+far-reaching+conclusions+from+one+specific+choice+of+model+without+a+substantive+justification+of+that+choice.&rft.publisher=WP-95-081&rft.date=1995-08&rft.type=Monograph&rft.type=NonPeerReviewed&rft.format=text&rft.language=en&rft.identifier=https%3A%2F%2Fpure.iiasa.ac.at%2Fid%2Feprint%2F4515%2F1%2FWP-95-081.pdf&rft.identifier=++MacKellar%2C+F.L.+%3Chttps%3A%2F%2Fpure.iiasa.ac.at%2Fview%2Fiiasa%2F2146.html%3E%2C+Lutz%2C+W.+%3Chttps%3A%2F%2Fpure.iiasa.ac.at%2Fview%2Fiiasa%2F190.html%3E+ORCID%3A+https%3A%2F%2Forcid.org%2F0000-0001-7975-8145+%3Chttps%3A%2F%2Forcid.org%2F0000-0001-7975-8145%3E%2C+Prinz%2C+C.+%3Chttps%3A%2F%2Fpure.iiasa.ac.at%2Fview%2Fiiasa%2F1520.html%3E%2C+%26+Goujon%2C+A.+%3Chttps%3A%2F%2Fpure.iiasa.ac.at%2Fview%2Fiiasa%2F110.html%3E+ORCID%3A+https%3A%2F%2Forcid.org%2F0000-0003-4125-6857+%3Chttps%3A%2F%2Forcid.org%2F0000-0003-4125-6857%3E++(1995).++Population%2C+Households%2C+and+CO2+Emissions.+++IIASA+Working+Paper.+IIASA%2C+Laxenburg%2C+Austria%3A+WP-95-081+++++