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.