More Oregon difference index from 2010 to 2020. The White-Black difference index increased from 0.2430 to 0.2695. The overall increase was small, and there was only a slight segregation between races. This may be due to the impact of housing prices, which led to some groups living in concentrated areas. The White-Asian difference index increased from 0.3331 to 0.3671, showing an upward trend. The White-Asian difference index is higher. Asians generally pay attention to education, so Asians will choose school districts with high square meters when choosing housing. This may have led to an increase in the difference index. The Black-Asian difference index decreased from 0.3068 to 0.2988, with an overall slight decrease. This may be due to the housing policies of some communities, which allow the two races to live together, resulting in a decrease in the difference index. The overall difference index of Hispanics-Non-Hispanic has dropped significantly, from 0.3548 to 0.309. The reason for the greater integration may be that the second-generation Hispanics have received English education since childhood, which makes it easier for them to integrate into the mainstream American group. More Hispanics have left the Hispanic community and integrated into the community of group races, making the difference index more integrated.

(group population ÷ total county population) × 100.

This turns raw population into percentages so every group is on the same 0 to 100 scale. We assume the census counted every resident only once, that 2010 and 2020 use the same race and ethnicity definitions, and that multiracial responses are handled the same way in both years. Next we measure how fast each group grew or shrank during the decade using Percent Change, given by

[(2020 group population ÷ 2010 group population) − 1] × 100.

This rate assumes the 2010 baseline is not zero and that no one was reclassified between censuses.

Applying the two formulas shows how the county actually changed. Between 2010 and 2020, Washington County added about 70,600 people. Roughly two-thirds of that increase came from Hispanic and Latino residents, about 46,900 people, and another third came from Asians, about 24,000. White-alone counts fell by around 20,200, so every bit of net growth came from minority groups. The combined non‑White share of the population rose from 23 percent in 2010 to 36 percent in 2020, a 13-point jump in just one decade. Multiracial responses nearly doubled, now topping 27,000, which explains part of the White decline. Washington County would likely become majority-minority sometime in the mid‑2030s if these growth rates continued. In short, the Percent of Total shows a quickly diversifying county, and the Percent Change singles out Hispanic or Latino and Asian communities as the main engines of that shift.

From this data, we can gather that over the next few decades, the population of Washington County is going to increase immensely. This can be due to many reasons such as an increase in jobs. Housing in Washington County may also be cheaper than housing in the city, Portland. It is also possible that over the decades, the birthrates in Washington County are higher than the death rates.

  n
H = - Σ [ (P_k/P) * ln (P_k/P) ]
          k=1

Looking at the broad racial category, Washington County, Oregon, has significantly diversified from 2010 to 2020, with the racial entropy increasing from 0.452 to 0.596.

The Hispanic population rose from 0.378 to 0.403, signaling a small increase and reflecting the rising presence of Hispanic origin groups. Still, Mexicans held the majority in 2010 and 2020, increasing by about 80%. During World War II, the bracero program was an agreement between the US and Mexico. This program aimed to temporarily contract Mexican farmers. This brought many Mexican workers to the US, specifically Washington County. After the program ended, many decided to stay. Though the most consistently diverse group is the Asian population, with an entropy score above 0.93 in both 2010 and 2020. This indicates an even distribution across all Asian ethnic groups. It is the second largest ethnic group after White non-Hispanics. Chinese immigrants played a crucial role in the construction of the transcontinental railroads. After the Chinese Exclusion Act of 1882, Chinese immigration dwindled, as well as other Asian ethnicities, because of xenophobic policies. Until the 1965 Immigration and Nationality Act removed racial discrimination against Asian people, allowing more Asians to immigrate.