The stock market has had an exceptionally good 2018 so far, with the Dow Jones Industrial Average having pushed even further into record territory recently. Various measures of economic strength in the U.S. have given favorable readings lately, and the newest came on Wednesday, as the private sector added roughly 230,000 jobs in September. That was the best reading since February, and it highlights just how important good employment activity has been for the economy overall. Market participants were also pleased about good news for several well-known individual companies. J.C. Penney (NYSE:JCP), Tempur Sealy International (NYSE:TPX), and Alcoa (NYSE:AA) were among the best performers on the day. Here's why they did so well.

J.C. Penney gets a new leader

Shares of J.C. Penney rose 4% after the beleaguered department store retailer announced that it had hired a new chief executive officer. Jill Soltau has a long history of working in the retail industry, having previously served as CEO of privately held fabric specialist Jo-Ann Stores, as well as working in high-level roles for other big-box department stores like Sears and Kohl's. For J.C. Penney, the move is an essential step forward following the departure of former chief executive Marvin Ellison, especially since its interim arrangement for leading the company had shown signs of fraying. Now, Soltau faces the tough task of helping J.C. Penney recover from years of difficult industry conditions.

Shopper with two J.C. Penney packages at the order pickup counter talking to a salesperson.

Image source: J.C. Penney.

Will Tempur Sealy be the last mattress company standing?

Tempur Sealy International stock climbed 11% in the wake of reports that one of the company's primary competitors will likely file for bankruptcy protection in the near future. Mattress Firm has had to deal with financial struggles for quite a while, as its brick-and-mortar retail locations have failed to generate the level of business that South African retailer Steinhoff International Holdings had expected when it acquired Mattress Firm in 2016. Tempur Sealy used to have a supply relationship with Mattress Firm, but the former terminated it in early 2017. Now, industry experts believe that a Mattress Firm bankruptcy, which would almost certainly involve store closures, could benefit Tempur Sealy by reducing competition in the mattress industry.

Alcoa benefits from price increases

Finally, shares of Alcoa gained 3%. The aluminum company gained ground in the wake of the decision of Norwegian competitor Norsk Hydro to close one of its refinery facilities in Brazil. The move from Norsk came after a period of running the refinery at half-capacity over the past six months, prompted by restrictions that Brazilian regulatory authorities have placed on the company. The resulting supply disruption had an immediate upward impact on global prices for alumina, one of the key ingredients that goes into aluminum production, and investors are optimistic that Alcoa can take advantage of more favorable market conditions for aluminum for as long as possible.

Dan Caplinger has no position in any of the stocks mentioned. The Motley Fool has no position in any of the stocks mentioned. The Motley Fool has a disclosure policy.