Walgreen (WAG) isn’t the only company under pressure, including by shareholders such as Goldman Sachs (GS), to move its headquarters overseas due to high U.S. taxation.

A number of other companies, about 15 since 1999, have also pulled up U.S. stakes, including the insurer Aon (AON), Weatherford International (WFT) and Actavis (ACT) (for more names, see below). Walgreen’s $16 billion buyout of Swiss-based Alliance Boots has put its lofty 37.5% corporate U.S. tax rate in the spotlight, versus the 20% rate now paid by Boots in Europe.

The trends are clear. As companies hoard cash due to economic uncertainty, taxes or regulation, their management is scrambling away from high U.S. taxes, as shareholder activists also bear down on them. The implications are also clear; tax corporations at ever higher rates and they’ll either spend shareholder capital to lower their effective rates with a lobbying army in D.C., raise prices, or move overseas, one of the most ineffective ways to solve income inequality since that middle-management layer, as well as entrepreneurs, leave the U.S. The same logic holds for tax the rich until there’s nothing left, then the middle class is next, or a value-added tax is unveiled (which one pundit joked that, for Washington, is like giving a drunk the keys to a liquor store). 

U.S. Trust put out a cheeky ranking showing Apple's (AAPL) corporate cash pile is more than the cash reserves of Malaysia, Turkey and Poland, while Microsoft (MSFT) outstrips Denmark, Israel, and the U.K., and Google’s (GOOG) cash holdings outpace Canada, Sweden, and Norway.

A recent study by the ratings agency Moody’s shows U.S. companies are sitting on a $1.64 trillion mountain of cash, with $947 billion parked offshore so as to avoid U.S. taxes.  That cash pile has turned companies into a cash-rich target for shareholder activists, recent analysis by PricewaterhouseCoopers’ Investor Resource Institute shows.

“Once an activist hedge fund’s interest in a company becomes public, the target company’s shareholder base often undergoes significant changes,” it says, as hedge funds and arbitrage investors move in. It also noted that “as much as 15% to 20%” of a targeted company’s “shareholder base may turn over.”

And companies are not always winning proxy fights. For the 12-month period ending in the third quarter of last year, company management won only 35% of proxy fights with activist hedge funds over board representation or control, down from 65% in 2010, according to FactSet. Pension funds and endowments have committed $7 billion to activist hedge funds in 2013 -- double what they invested a year before, PwC’s Investor Resource Institute notes.

Standard & Poor’s also found that, as the top 1,100 U.S. companies have seen their cash piles increase to $1.23 trillion, they also have tripled their borrowings over the last three years to a gross $4 trillion, while keeping their cash overseas to avoid taxation. These companies, including Apple, Microsoft, Merck (MRK), Chevron (CVX) and Cisco (CSCO), have borrowed to appease investors, including activist shareholders, with dividend increases and stock buybacks.  

The question now is, will the largest drugstore chain in the U.S., Walgreens, join these companies who have moved their headquarters overseas, escaping U.S. taxes? 

Here’s a rundown of some other companies that have moved their U.S. headquarters, from William McBride, analyst with the Tax Foundation:

Actavis (buying Forest Labs for $25 billion) – Ireland 

Applied Materials - Netherlands

Aon – UK

Eaton Corp. – Ireland

Foster Wheeler - Switzerland

Ensco International  – UK

Nabors Industries – Bermuda

Noble Corp. – UK

Omnicom – Netherlands

Perrigo – Ireland

Transocean – Switzerland

Weatherford International  - Switzerland

Elizabeth MacDonald joined FOX Business Network (FBN) as stocks editor in September 2007 and is the author of Skirting Heresy: The Life and Times of Margery Kempe (Franciscan Media, June 2014).
Follow Elizabeth MacDonald on Twitter @LizMacDonaldFOX.