What accounts for the rise in the participation rate in the United States and the euro zone?

The current rise in the participation rate (in the proportion of the working-age population in the labour market) is playing a key role in the United States and the euro zone. It is enabling growth to continue and stop ping the low unemployment rate from driving up inflation. But what accounts for this rise in the participation rate? Which age bracket? The return to the labour market of people who had left it, or the arrival in the labour market of people who had not previously participated? The appeal of higher wages? It is being caused primarily by a rising participation rate among over-50s and can be attributed to the acceleration in real wages. Given the above, by how much more could the participation rate rise? This is a very important question, because if the participation rate stops rising, growth will fall and inflation will rise. It seems that significant potential remains for the participation rate to rise in the United States and the euro zone.