How do we know the Kingdom is expanding ?

The Kingdom of God was first given to Adam and Eve and their children, but sadly, they forfeited it to Satan.

Do you not know that if you present yourselves to anyone as obedient slaves, you are slaves of the one whom you obey, either of sin, which leads to death, or of obedience, which leads to righteousness? Romans 6:16 ESV

The blessing was then given to Abraham and his family to pass on to every ethnic group.

Now the Lord said to Abram, “Go from your country and your kindred and your father’s house to the land that I will show you. And I will make of you a great nation, and I will bless you and make your name great, so that you will be a blessing. I will bless those who bless you, and him who dishonors you I will curse, and in you all the families of the earth shall be blessed.”
Genesis 12:1-3a ESV

We Gentiles have been invited to join that family.

For as many of you as were baptized into Christ have put on Christ. There is neither Jew nor Greek, there is neither slave nor free, there is no male and female, for you are all one in Christ Jesus. And if you are Christ’s, then you are Abraham’s offspring, heirs according to promise.
Galatians 3:27-29 ESV

Since Jesus’ resurrection when there were approximately 120 devoted followers of Jesus, the Kingdom of God has expanded to about 2.4 billion followers. In Africa alone the Church is expanding by 33,000 every day. It’s believed that China has between 80 and 100 million believers. This is a fulfillment of Jesus’ prophetic parables.

He put another parable before them, saying, “The kingdom of heaven is like a grain of mustard seed that a man took and sowed in his field. It is the smallest of all seeds, but when it has grown it is larger than all the garden plants and becomes a tree, so that the birds of the air come and make nests in its branches.” He told them another parable. “The kingdom of heaven is like leaven that a woman took and hid in three measures of flour, till it was all leavened.”
Matthew 13:31-33 ESV