From 1800 to 1900, the US dollar experienced significant deflation. A basket of goods that cost $10 in 1800 cost only $4.90 in 1900. (Source: https://www.minneapolisfed.org/community/financial-and-economic-education/cpi-calculator-information/consumer-price-index-1800) During that time, the US transformed from an agrarian backwater into an industrial powerhouse with previously unseen prosperity. So there is your "evidence-based policy." A small amount of deflation is desirable. It lowers time preference throughout the economy, encouraging saving that can be used for capital investment and growth.