you are a bit out of whack there... these are figures for home owners (the renters are allowed to have larger sums for assets but those assets would be earning an income, thereby reducing their pension)
pension for singles 712, for couples 573 each.... is not 2 times... couples receive 75% each of the single pension but think about the electricity costs of running a home today assets for singles is 192500 for couples its 273000 , that is the combined amount
they assume 2 can live cheaper than one....thats about all