The most recently tallied retirement savings numbers show Americans’ savings assets totaled $16.6 trillion at the end of the first quarter of this year.

The numbers, which come from the Investment Company Institute, also show that retirement savings account for 38 percent of all household financial assets.

The news makes March of this year a high-water point in American retirement savings, as assets for 2006 amounted to $16.4 trillion.

Individual retirement accounts and defined contribution plans factored into the retirement savings growth, with first-quarter IRAs growing to $4.4 trillion from $4.2 trillion during the first quarter and defined contribution plans growing from $4.1 trillion to $4.2 trillion during the same period.

In other categories, totals remained unchanged from 2006: government pension plans stood at $4.2 trillion, private benefit plans at $2.3 trillion, and annuities at $1.3 trillion.