According to Robert Shiller and his book Irrational Exuberance, the historical average dividend yield for the S&P 500 between 1870 and 2013 is about 4.4%. On a compounding basis with all of your stipends reinvested, you could double your capital on the dividend alone in a hair over 16 years at this yield.

G
Source: Robert Shiller, Irrational Exuberance.

Currently, though, we're a far cry from that with the yield on the S&P 500 coming it at a paltry 1.93%. With interest rates remaining low -- thus keeping CD and bond yields to a minimum -- the search for yield and dividend growth remains a top priority for many investors.

Within the health care sector, there are 76 dividend-paying companies. As you might expect, with high margins to be made on branded drugs and rapidly growing prescription costs, some health care companies are literally swimming in cash flow. A good chunk of health care companies that fit this mold are doing a great job of rewarding their shareholders with premium dividends.

However, some health care companies aren't anywhere near their full potential when it comes to paying out a dividend. Here are five health care companies that I believe are currently shortchanging their shareholders on the dividend front that could and should raise their dividend.

Allergan (NYSE:AGN) – 0.22% yield
When I think of Allergan's paltry $0.05 per quarter dividend, I have visions in my head of Dr. Evil talking to his henchmen saying, "Throw me a bone here!" On one hand, Allergan has certainly seen its fair share of flops recently with inhaled migraine medication Levadex (acquired when it purchased MAP Pharmaceuticals) receiving its second complete response letter, experimental vision-loss drug DARPin underwhelming in mid-stage trials, and the Food and Drug Administration giving clearance to allow a generic form of Restasis to potentially hit the market without human trials.

Yet, even with these disappointments factored in, Allergan has grown its revenue on an annual basis by 14% since 2004 but hasn't raised its dividend once! Added up, Allergan has paid out less than $500 million in dividends since its last dividend increase but has brought in a whopping $5.6 billion in free cash flow over that time period. If Allergan is to become a more intriguing investment, it should seriously consider a dividend increase.

CIGNA (NYSE:CI) -- 0.05% yield
Could they spare it? That 0.05% yield is not a misprint! CIGNA, one of the nation's largest individual and employer-based health insurers, has paid out a combined $0.30 in dividends over the past eight years. Over that same time frame, it also earned a cumulative $32.59 in EPS for an eight-year payout ratio of (drumroll, please) 0.92%! Pitiful!

There's certainly some trepidation moving forward with the passage of the Patient Protection and Affordable Care Act and how that might affect insurers considering the new 80% medical loss ratio cap. Then again, CIGNA's purchase of Healthspring will allow it to pull in potentially hundreds of thousands of newly insured government-sponsored members (i.e., Medicaid approved), and the push toward corporate privatization may help it gain new members as well. There is absolutely no reason why CIGNA couldn't be paying out somewhere in the neighborhood of $0.50-$1 annually. Until such time as CIGNA does decide to reward its shareholders perhaps shareholders should look elsewhere in this space.

Thermo Fisher Scientific (NYSE:TMO) -- 0.64% yield
Unlike the previous two companies, I'm going to give Thermo Fisher a bit of a break given that it did start paying a dividend only two years ago and it's in the midst of purchasing genetic analysis device and service provider Life Technologies for a whopping $13.6 billion. The move will help diversify Thermo Fisher's product line, should be accretive to its earnings almost immediately, and will position the company for big growth in the coming decade as personalized health care takes off and baby boomers age.

Still, I can't help but overlook the fact that over the past six years Thermo Fisher Scientific has averaged nearly $1.4 billion in annual free cash flow but is paying out only around $200 million in dividends each year. With a payout ratio of just 11% of forecasted 2013 EPS, Thermo Fisher would be wise to up its payout once the Life Technologies deal closes otherwise it may fail to attract long-term income-seeking investors.

Zoetis (NYSE:ZTS) -- 0.80% yield
Like Thermo Fisher, Zoetis is a newbie when it comes to paying a dividend. Zoetis is the animal health division spun off by Pfizer earlier this year that's grown revenue by an average of 16.3% over the past three years. It's not hard to understand why investors got so excited about this spinoff as it's the first animal health pure-play in the pharmaceutical field. On paper, Zoetis makes a lot of sense as an investment with more people than ever owning pets and the cost of animal health care rising in accord with human health care costs.

Deep down, though, I sure hope Zoetis has a dividend increase in its cards. Currently, Zoetis is paying out only 19% of its projected 2013 EPS, which is a far cry from what its former parent, Pfizer, typically pays out. R&D expenses do act as somewhat of a constraint on cash flow, but I nonetheless see no reason why Zoetis couldn't pay out at least $0.40-$0.45 on an annualized basis.

Perrigo (NYSE:PRGO) -- 0.29% yield
Last, but certainly not least is branded drug and over-the-counter drugmaker Perrigo, which, like Thermo Fisher, is in the midst of a sizable buyout. Perrigo is looking to expand its pipeline and boost its cash balance all while enjoying the tax breaks that Ireland has to offer by purchasing Elan for $8.6 billion. While I have personally questioned Perrigo's need to pay out the nose for Elan's dilapidated pipeline, it's hard to argue with Perrigo's average annual growth rate of 14.7% over the past decade.

What I can't overlook is Perrigo's paltry payout ratio which is averaging less than 8% of its EPS since 2011 despite the company boosting its dividend in each year. What Perrigo really needs to excite shareholders beyond the Elan deal is a sizable dividend increase. Having generated $450 million in free cash flow in fiscal 2013, I see no reason why Perrigo couldn't afford a dividend of $1 or perhaps even more per year.

Fool contributor Sean Williams has no material interest in any companies mentioned in this article. You can follow him on CAPS under the screen name TMFUltraLong, track every pick he makes under the screen name TrackUltraLong, and check him out on Twitter, where he goes by the handle @TMFUltraLong.

The Motley Fool recommends Thermo Fisher Scientific. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.