Twenty-eight of the nation’s elite colleges and universities—including all the Ivy League schools except for Princeton and Harvard—announced an agreement last Friday to boost financial aid to their neediest students.

The wide-ranging new guidelines are an attempt to arrest a trend of giving aid to the most desirable students rather than those who need the money most.

So-called “merit aid” has made it harder for students from low- and middle-income families to attend college, since aid has not necessarily been focused on those who financially need it, according to financial aid officials.

Thus Friday’s agreement, signed largely by universities and colleges that admit students without regard to their ability to pay, will go a long way towards increasing socio-economic diversity at those colleges, the signers said.

The recommendations include:

• Institutions will take into account the higher cost of living in cities like New York and San Francisco.

• They will take into account the greater financial liabilities faced by parents who are not covered by formal retirement plans.

• They will only consider two guardians for children from separated or divorced families, instead of the traditional consideration of all four possible parents and step-parents.