What: Shares of Prudential Financial (PRU 0.06%), Lincoln Financial (LNC 1.31%), and Manulife Financial (MFC 0.68%) are all dropping today, trading down more than 10% at 3 p.m. ET.

Prudential Financial and Manulife Financial are falling after earnings misses, with Lincoln National likely taking a sympathy dive on a day in which life insurers are getting cold reception from investors.

So what: After the market close on Wednesday, Prudential Financial reported disappointing fourth-quarter results. The company reported that operating earnings fell about 12%, and investment income failed to live up to analyst expectations. Prudential's operating earnings of $1.94 per share fell below analyst expectations for $2.30 per share.

Likewise, Manulife Financial was similarly hard hit. The company reported that its net income plunged to $246 million (Canadian dollars), or $0.11 per share, down from $0.33 per share in the year-ago period. So-called "core earnings" per common share fell to $0.42, failing to meet Bloomberg's consensus estimate of $0.45 per share.

Interestingly, Manulife's disappointing earnings could be partly blamed on trouble in the oil sector. The company noted that it took a charge of $876 million related to investments in the oil and gas industry. In its release, it warned that if oil and gas prices remain at current levels, it expects there could be secondary impacts to its debt and real estate portfolios, in addition to direct negative impacts to its oil and gas-related investments.

Lincoln Financial called out "lower alternative investment income" as a reason for its lower life insurance earnings when the company reported its fourth-quarter results last week. It also distanced itself from oil investments on its conference call, with one executive noting that the company "stopped investing in the energy sector a year ago." It also made a point to announce that of its $8.6 billion energy portfolio, only $600 million was invested in high-yield (riskier) energy assets on the call. 

Now what: The macroeconomic environment is increasingly affecting insurers of all types, particularly life insurers. Life insurance and annuity companies rely on long-term investments to generate sufficient returns to pay claims. Premiums from long-term insurance contracts are invested in everything from bonds to common stocks.

Today, that presents a bit of a problem. Despite an increase in short-term rates thanks to the Fed's quarter-point increase in rates last year, long-term rates have dropped precipitously. Today, a 30-year U.S Treasury bond yields just 2.5%, compared to its 2015 peak of 3.25%.

In many ways, life insurers are as much asset managers as they are insurance companies. As markets decline, life insurers write down the value of their investment portfolios at the same time their asset management units generate fewer fees on investment products sold to clients. If stock prices and bond yields continue to fall, expect life insurers to continue to disappoint.