On Feb. 24, Warren Buffett's Berkshire Hathaway (NYSE:BRK-A)(NYSE:BRK-B) will report earnings for the fourth quarter of 2017, and release Buffett's widely read letter to shareholders describing the past year and his expectations for many years ahead.

Berkshire may have its hands in everything from paints to airplane parts, but its earnings power is concentrated in a few key business segments. Here are five things worth paying particular attention to.

1. Risky business

Berkshire's insurance businesses have historically been an important part of its earnings power, but 2017 is likely to be a year they'd prefer to forget. Barring a miracle in the fourth quarter, Berkshire's insurers are set to produce an underwriting loss over a full calendar year. The last time Berkshire reported a full-year underwriting loss was 2002.

Warren Buffett at the annual shareholder's meeting.

Image source: The Motley Fool.

But don't feel too bad for Berkshire Hathaway. A single bad quarter, or even a bad year, isn't entirely unexpected from an insurance company. Berkshire's insurers were negatively affected by large hurricane losses (Hurricanes Harvey, Irma, and Maria) and an earthquake in Mexico. Luckily, other insurers that have already reported fourth-quarter earnings have revealed an accounting period mostly devoid of large losses, though wildfires in California were blamed for some insurers' rising loss ratios.

The prospects for Berkshire's insurers look better in 2018. Its insurance companies stand to benefit from reduced corporate taxes, and could see favorable price increases as competitors retrench after taking large storm losses in 2017.

2. Riding the rails

Berkshire's BNSF railroad makes its money from the relatively simple business of moving "stuff" all around the country. But railroads can be very cyclical -- like in 2016 when BNSF's profits dipped due to a decline in energy-related commodity shipments.

In 2017, the story for railroads was a recovery in coal prices and coal carloads, helping propel railroads out of their 2016 doldrums. Berkshire last reported that BNSF's coal-related shipping revenue grew by nearly 21% over the prior-year period in the first nine months of the year.

However, coal is unlikely to be a major earnings driver this quarter. BNSF's carload report for the fourth quarter shows a 8.7% decrease in coal volumes compared to the year-ago period. Other types of shipments picked up the slack, as combined intermodal and carload volume increased by 3.8% compared to the same period the year before.

We'll have to wait for the earnings report to see how the pricing mix panned out for BNSF, but a healthy single-digit increase in overall volume is very good to see.

3. Manufacturing money

Manufacturing, service, and retailing businesses now make up the largest portion of Berkshire's operating profit. Within this group, the industrial businesses including Lubrizol, IMC, and Precision Castparts, drive the bulk of its profits.

The industrial companies are not fast growing by any means -- Precision Castparts and Lubrizol reported revenue growth of about 2% in the first nine months of 2017 compared to the prior-year period -- but they are extraordinarily profitable, earning beefy pre-tax profit margins in excess of 17% in the first nine months of the year. Its industrial units primarily grow by way of acquisition, rolling up smaller companies under their umbrella. Buffett typically shines a light on Berkshire's smaller acquisitions in his letter to shareholders.

Within the retail segment, investors should look forward to any additional detail surrounding Berkshire's fourth-quarter investment in Pilot Flying J. Berkshire announced it would acquire 38.6% of the truck stop chain, and increase its ownership stake to 80% of the company in 2023. It's Berkshire's second big bet on cars and personal transportation in recent years, joining Berkshire Hathaway Automotive, a holding company for 110 dealerships across the United States.

4. The windmills keep on turning

Berkshire Hathaway Energy is as reliable as it gets. Because it earns its revenue and profit primarily from the sale of power in regulated markets, it earns a reliable, if unexciting, stream of earnings quarter after quarter. This isn't a segment known for its surprises.

What matters most for Berkshire Hathaway Energy isn't how much it earns now, but how much Buffett is willing to deploy to grow it by acquisition. The energy unit has become a sponge for Berkshire's excess cash, a place where Berkshire can put money to work to earn a relatively safe, but attractive, return.

Berkshire has pursued large deals in energy recently, narrowly missing out on a $9 billion deal to acquire Oncor in 2017. We'll see what Buffett has to say about that deal, and the opportunity set as a whole. With cash piling up, utilities are one place where Buffett can still put a lot of money to work in one fell swoop.

5. A book value boom

Berkshire is almost certain to be a star on at least one metric: book value growth. Thanks to the passage of the Tax Cut and Jobs Act, which reduced the statutory corporate tax rate from 35% to 21%, Berkshire will see an immediate surge in its book value.

Buffett often talks about how Berkshire defers paying taxes on its stock gains by selling stocks sparingly. But even though Berkshire may avoid paying taxes in cash, it has to measure the liability and record it on its balance sheet. Of course, with tax rates dropping to 21% from 35%, the amount Berkshire has to record as a deferred tax liability should drop in kind. That should power a big jump in book value, as Barclays' analyst Jay Gelb previously estimated that such a change could result in a 9% increase in Berkshire's book value.

The change in tax rates may explain why Berkshire sold off most of its IBM stake in 2017. A loss harvested against income taxed at 35% is much more valuable than a loss harvested against income taxed at 21%. But if all this tax talk puts you to sleep, just know that Buffett hasn't skipped a beat in maximizing his shareholders' after-tax returns.

Jordan Wathen has no position in any of the stocks mentioned. The Motley Fool owns shares of and recommends Berkshire Hathaway (B shares). The Motley Fool has a disclosure policy.