The plummet in gasoline prices over the last two-years has yielded a welcome windfall to American consumers. It had been thought that consumers split the extra money evenly between additional spending and savings. However, new evidence suggests that, with regard to the gasoline windfall, spending swamps saving.

The windfall is averaging $700 per household in 2015, according to a study just released by the JPMorgan Chase Institute. Researches gauged the spending behavior attributable to the 45 percent decrease in gasoline prices from early 2014 to early 2015. Prices peaked at $3.70 per gallon in April of 2014, but have since dropped and hit a low of roughly $2.20.

The study investigates who benefits the most and how the extra money is used. The surprise is that Americans are spending about 80 percent of the windfall, not the 50 percent previously thought. Consumers are using this boost in discretionary income for purchases well beyond gasoline.

The Institute made four major findings:

1. Gas spending and savings: When prices were peaking in early 2014, the average American's gasoline bill was $101 per month. The top 20 percent of gas spenders shelled out $359/month via debit and credit cards, three times the national average.

On the other hand, the bottom 20 percent of gas spenders forked over only two bucks a month, creating a 150X spread between the top and bottom quintiles. In 2015, the average American is saving $22 a month on gasoline, but the results vary widely. About 16 percent have increased their gas spending by at least 50 percent, whereas 23 percent are cutting expenditures at the gas pump by 50 percent.

2. Geographic Distribution: Consumers on the East and West Coasts are enjoying less of a windfall because they had been spending less on gas, compared to folks in the South and Midwest, the so-called "high-impact" regions. People in low-impact states paid higher prices but bought less gasoline, whereas consumers in high-impact regions enjoyed lower prices but bought more gas.

3. Age, Gender and Income Level: For low-income Americans, the gasoline windfall amounted to more than 1 percent of their monthly income. Younger Americans benefited more than their elders did.

The biggest spenders were high-income men in the 30-49-year-old cohort, but 18-29-year-old low-income men felt the biggest percentage impact. When gas prices cratered in January 2015, low-income men reaped savings of 1.6 percent, with credit/debit card sales accounting for 1.1 percent.

The highest income quintile experienced an increase of only 0.5 percent in its purchasing power.

4. Consumer Spending: Consumers stashed only about 20 percent of their gas windfalls into savings. The biggest recipients of the remaining 80 percent were restaurants, department stores, entertainment venues and electronics/appliance sellers.

The study sampled 25.6 million of Chase's regular card users and 1 million "core" customers from a pool of 57 million anonymized debit/credit card holders. The sampled customers average at least five monthly checking account transactions, and the core customers do not hold a brand-specific gas-station charge card.