The million dollar club is becoming less exclusive, as the number of millionaire households in the U.S. has risen 56 percent since 2003, reaching 5.4 million, according to a new report.

The results, released Friday by Phoenix Marketing International, qualify a millionaire household as one having at least $ 1 million in liquid or "investable' assets.

The extraordinary gains in the millionaire households population in the past three years is a function of their asset allocations and access to products that can maximize market gains,' said David M. Thompson, Vice President at PMI.

Over the same period, PMI says number of penta-millionaire households have increased 47 percent to 755,000 in the same period.

The global number high net worth individuals (HNWI), people with net financial assets of at least $1 million, excluding their primary residence and consumables, rose 6.5 percent to 8.7 million in 2005, over 2004, according to the 2006 World Wealth Report from Capgemini and Merrill Lynch.