Possessives: Joint or Separate Ownership

Recently a subscriber wrote to ask which of these two constructions is correct:

The administrative assistant completed John’s and Rob’s report.
The administrative assistant completed John and Rob’s report.

In cases of joint ownership, only the second (or last) noun or pronoun has to be possessive, but in cases of separate ownership, both (or all) nouns or pronouns are possessive.

Thus, assuming that the report belongs to both John and Rob, the correct construction is the second one. If, however, each person has a separate report, then both names would be possessive and the word report would need to be plural:

The administrative assistant completed John’s and Rob’s reports.

Here are some additional examples followed by explanations:

We are planning to attend Sam and Teresa’s retirement party. (One party is being held to celebrate both people’s retirement, so the party “belongs,” so to speak, to them jointly.)
We are planning to attend the party honoring Sam’s and Teresa’s outstanding sales records. (Each of them possesses a separate, individual sales record; the records are not jointly owned.)

When I went to my husband’s family reunion, I finally met Joe’s and Martha’s parents. (Joe and Martha are not siblings and thus do not “own” the same set of parents.)
When I went to my husband’s family reunion, I finally met Tim and Sally’s parents. (Tim and Sally are siblings and thus “own” the same set of parents.)

TEST YOURSELF

1. We complained to the housekeeping service when the trash receptacles in Hal and Barb’s offices had not been emptied for three days. [They work in separate offices.]
2. Smallville and Eden’s population increases in the last decade have been staggering, despite economic hardships endured by both counties.
3. After the ceremony, everyone who attended Nancy’s and Tom’s wedding walked across the street to the reception.
4. Susan and Richard’s proposals were outstanding, so the company has funded both of the projects for the next fiscal year.
5. The seamstress had to alter both Emily and Julie’s dress before the party.

ANSWERS

1. Hal’s and Barb’s offices
2. Smallville’s and Eden’s population increases
3. Nancy and Tom’s wedding
4. Susan’s and Richard’s proposals
5. Emily’s and Judy’s dresses