Mid-cap stocks often strike the right balance between having proven business models and market opportunities that can support $100 billion corporations. However, they face intense competition from scaled industry giants and can be disrupted by new innovative players vying for a slice of the pie.

These dynamics can rattle even the most seasoned professionals, which is why we started StockStory - to help you separate the good companies from the bad. That said, here are three mid-cap stocks to avoid and some other investments you should consider instead.

AECOM (ACM)

Market Cap: $13.69 billion

Founded in 1990 when a group of engineers from five companies decided to merge, AECOM (NYSE: ACM) provides various infrastructure consulting services.

Why Does ACM Fall Short?

1. Demand cratered as it couldn’t win new orders over the past two years, leading to an average 2.7% decline in its backlog
2. Sales are projected to tank by 2.5% over the next 12 months as demand evaporates
3. Subpar operating margin of 4.7% constrains its ability to invest in process improvements or effectively respond to new competitive threats

At $102.91 per share, AECOM trades at 19x forward P/E. Read our free research report to see why you should think twice about including ACM in your portfolio.

TransUnion (TRU)

Market Cap: $16.03 billion

One of the three major credit bureaus in the United States alongside Equifax and Experian, TransUnion (NYSE: TRU) is a global information and insights company that provides credit reports, fraud prevention tools, and data analytics to help businesses make decisions and consumers manage their financial health.

Why Are We Hesitant About TRU?

1. Efficiency has decreased over the last five years as its adjusted operating margin fell by 3.5 percentage points
2. Free cash flow margin dropped by 10 percentage points over the last five years, implying the company became more capital intensive as competition picked up
3. ROIC of 5.9% reflects management’s challenges in identifying attractive investment opportunities, and its shrinking returns suggest its past profit sources are losing steam

TransUnion’s stock price of $85.58 implies a valuation ratio of 17.7x forward P/E. Check out our free in-depth research report to learn more about why TRU doesn’t pass our bar.

Unum Group (UNM)

Market Cap: $12.66 billion

Tracing its roots back to 1848 when financial security for workers was virtually non-existent, Unum Group (NYSE: UNM) provides workplace financial protection benefits including disability, life, accident, critical illness, dental and vision insurance primarily through employers.

Why Do We Think Twice About UNM?

1. Net premiums earned only expanded by 2.7% annually over the last five years, trailing its insurance peers as its scale limited incremental business
2. Earnings per share lagged its peers over the last two years as they only grew by 6.2% annually
3. Sizable asset base leads to capital growth challenges as its 3.8% annual book value per share increases over the last five years fell short of other insurance companies

Unum Group is trading at $76.97 per share, or 1.1x forward P/B. If you’re considering UNM for your portfolio, see our FREE research report to learn more.

Stocks We Like More

Your portfolio can’t afford to be based on yesterday’s story. The risk in a handful of heavily crowded stocks is rising daily.

The names generating the next wave of massive growth are right here in our Top 6 Stocks for this week. This is a curated list of our High Quality stocks that have generated a market-beating return of 244% over the last five years (as of June 30, 2025).

Stocks that made our list in 2020 include now familiar names such as Nvidia (+1,326% between June 2020 and June 2025) as well as under-the-radar businesses like the once-micro-cap company Tecnoglass (+1,754% five-year return). Find your next big winner with StockStory today for free. Find your next big winner with StockStory today. Find your next big winner with StockStory today

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