Did you read the whole article? I do not think sharply and modestly are the same description.
Implications
Preliminary results from the first 19 days of January show the U.S. uninsured rate has modestly declined since the health insurance mandate went into effect at the beginning of the year. The uninsured rate has fluctuated at other points over the past several years, so it is unclear if this small decline is a reflection of the provisions of the Affordable Care Act that took effect on Jan. 1, or if this is part of a trend based on other reasons.
Still, with only 2.1 million Americans newly enrolled in plans through the exchanges as of Dec. 28, 2013, the Obama administration and other proponents of the new healthcare law have a long way to go in hopes of reaching the goal of increasing the number of Americans who have health coverage.
Gallup will continue to track the U.S. uninsured rate in the weeks and months ahead.
I see this as a result of the expansion of medicaid. The biggest change is in unemployed. Yes, this is a result of ACA, but you did not have to create such a massive law to simply increase the eligibility of medicaid. Honestly, am I misreading the article you posted?