"We define purchasing power as the **quantity of wheat a worker can buy with a weekly salary**, which varies with time. "
"We define purchasing power as the **quantity of wheat a worker can buy with a weekly salary**, which varies with time. Playfaire wants to prove that workers' purchasing power had increased with time, and the purchasing power - year graph has also shown a trend that purchasing power is growing."
"Think about another method to present the advancement of time, to prove that workers' purchasing power increasing with time."
"Think about another method to present the advancement of time, to prove that workers' purchasing power increasing with time: applying a **10 years mean on purchasing power**, so we can see it works better or not?"